Image coding method, image decoding method, image coding apparatus, image decoding apparatus, and image coding and decoding apparatus

ABSTRACT

An image coding method in which a chroma component and a luma component of an input image including one or more transform blocks are transformed to code the input image. The luma component has the same size as the current transform block. The chroma component is smaller than the current transform block. In the method, when the current transform block has a first minimum size, the chroma component is transformed on a basis of a block resulting from binding a plurality of the chroma blocks to has the same size as the luma block, and when the current transform block has a size other than the first minimum size, a CBF flag indicating whether or not coefficients of the chroma component include a non-zero coefficient is not coded.

CROSS REFERENCE TO RELATED APPLICATIONS

This is a continuation of application Ser. No. 15/042,410, filed Feb.12, 2016, which is a continuation of application Ser. No. 14/609,811,filed Jan. 30, 2015, now U.S. Pat. No. 9,326,005, which is acontinuation of application Ser. No. 14/018,657, filed Sep. 5, 2013, nowU.S. Pat. No. 9,031,334, which claims the benefit of U.S. ProvisionalPatent Application No. 61/698,765, filed Sep. 10, 2012. The entiredisclosures of the above-identified applications, including thespecifications, drawings and claims are incorporated herein by referencein their entirety.

FIELD

The present disclosure relates to an image coding method for imagecoding or an image decoding method for image decoding.

BACKGROUND

A technique relating to an image coding method for coding an image(which may be a moving picture) or an image decoding method for decodingsuch an image is discussed in Non Patent Literature 1.

CITATION LIST Patent Literature Non Patent Literature

-   [Non Patent Literature 1] ISO/IEC 14496-10 “MPEG-4 Part 10: Advanced    Video Coding”

SUMMARY Technical Problem

However, there is a problem that the image coding method or imagedecoding method according to conventional art has insufficient codingefficiency.

In view of this, the present disclosure provides an image coding methodand an image decoding method which have increased coding efficiency.

Solution to Problem

An image coding method according to an aspect of the present disclosureis an image coding method of coding an input image including one or moretransform blocks each having a luma component and a chroma component,the luma component being to be processed on the basis of a luma blockwhich belongs to a current one of the one or more transform blocks andhas the same size as a size of the current transform block, the chromacomponent being to be processed on the basis of a chroma block whichbelongs to the current one of the one or more transform blocks and has asize smaller than the size of the luma block, and the image codingmethod including: deriving coefficients of the luma component byperforming transform on the luma component and deriving coefficients ofthe chroma component by performing transform on the chroma component;and coding the coefficients of the luma component and the coefficientsof the chroma component, wherein in the deriving, when the size of thecurrent transform block is a predetermined first minimum size, thecoefficients of the chroma component are derived by performing thetransform on the chroma component on the basis of a block resulting frombinding a plurality of the chroma blocks, the resulting block having thesame size as the size of the luma block, and in the coding, when thesize of the current transform block is the first minimum size, a flagindicating whether or not the coefficients of the chroma componentinclude a non-zero coefficient is not coded, and when the size of thecurrent transform block is a size other than the first minimum size, theflag is coded.

An image decoding method according to an aspect of the presentdisclosure is an image decoding method of decoding, from a codedbitstream, an image including one or more transform blocks each having aluma component and a chroma component, the luma component being to beprocessed on the basis of a luma block which belongs to a current one ofthe one or more transform blocks and has the same size as a size of thecurrent transform block, the chroma component being to be processed onthe basis of a chroma block which belongs to a current one of the one ormore transform blocks and has a size smaller than a size of the lumablock, and the image decoding method including: decoding coefficients ofthe luma component and coefficients of the chroma component which arecoded and included in the coded bitstream; and deriving the lumacomponent by performing transform on the coefficients of the lumacomponent and deriving the chroma component by performing transform onthe coefficients of the chroma component, wherein in the deriving, whenthe size of the current transform block is a predetermined first minimumsize, the coefficients of the chroma component are derived by performingthe transform on the chroma component on the basis of a block resultingfrom binding a plurality of the chroma blocks, the resulting blockhaving the same size as the size of the luma block, and in the decoding,when the size of the current transform block is a size other than thefirst minimum size, a flag indicating whether or not the coefficients ofthe chroma component include a non-zero coefficient is decoded.

The general or specific aspect may be implemented using a system, amethod, an integrated circuit, a computer program, or acomputer-readable recording medium such as a CD-ROM, or any combinationof systems, methods, integrated circuits, computer programs, orcomputer-readable recording media.

Advantageous Effects

The image coding method and image decoding method according to thepresent disclosure enables coding with increased efficiency (a reducedamount of codes).

BRIEF DESCRIPTION OF DRAWINGS

These and other objects, advantages and features of the invention willbecome apparent from the following description thereof taken inconjunction with the accompanying drawings that illustrate a specificembodiment of the present invention.

FIG. 1 is a block diagram showing an example of a configuration of animage coding apparatus in Embodiment 1.

FIG. 2 is a block diagram showing an exemplary configuration of aquadtree coding unit in Embodiment 1.

FIG. 3 is a flowchart showing an example of steps of an image codingmethod in Embodiment 1.

FIG. 4 shows an example of splitting of a largest coding unit (LCU) intocoding units (CUs).

FIG. 5 shows an example of CU split flags corresponding to the LCU shownin FIG. 4.

FIG. 6 shows an example of splitting of the LCU shown in FIG. 4 intoTUs.

FIG. 7 shows an example of TU split flags corresponding to the LCU shownin FIG. 6.

FIG. 8 is a flowchart showing an example of operation of a quadtreecoding unit.

FIG. 9 is a flowchart showing an example of operation of a CU codingunit of the quadtree coding unit shown in FIG. 3.

FIG. 10 is a flowchart showing an example of operation of a quadtreetransform unit of the CU coding unit shown in FIG. 3.

FIG. 11 is a flowchart showing an example of operation of a TU codingunit of the quadtree transform unit shown in FIG. 3.

FIG. 12 shows an example of CBF_Cb corresponding to a TU in FIG. 7.

FIG. 13 is a block diagram showing an example of a configuration of animage decoding apparatus in Embodiment 2.

FIG. 14 is a block diagram showing an exemplary configuration of aquadtree decoding unit in Embodiment 2.

FIG. 15 is a flowchart showing an example of steps of an image decodingmethod in Embodiment 2.

FIG. 16 is a flowchart showing an example of operation of a quadtreecoding unit shown in FIG. 14.

FIG. 17 is a flowchart showing an example of operation of a CU decodingunit shown in FIG. 14.

FIG. 18 is a flowchart showing an example of operation of a quadtreetransform unit shown in FIG. 14.

FIG. 19 is a flowchart showing an example of operation of a TU decodingunit shown in FIG. 14.

FIG. 20 shows an overall configuration of a content providing system forimplementing content distribution services.

FIG. 21 shows an overall configuration of a digital broadcasting system.

FIG. 22 shows a block diagram illustrating an example of a configurationof a television.

FIG. 23 shows a block diagram illustrating an example of a configurationof an information reproducing/recording unit that reads and writesinformation from and on a recording medium that is an optical disk.

FIG. 24 shows an example of a configuration of a recording medium thatis an optical disk.

FIG. 25A shows an example of a cellular phone.

FIG. 25B is a block diagram showing an example of a configuration of acellular phone.

FIG. 26 illustrates a structure of multiplexed data.

FIG. 27 schematically shows how each stream is multiplexed inmultiplexed data.

FIG. 28 shows how a video stream is stored in a stream of PES packets inmore detail.

FIG. 29 shows a structure of TS packets and source packets in themultiplexed data.

FIG. 30 shows a data structure of a PMT.

FIG. 31 shows an internal structure of multiplexed data information.

FIG. 32 shows an internal structure of stream attribute information.

FIG. 33 shows steps for identifying video data.

FIG. 34 shows an example of a configuration of an integrated circuit forimplementing the moving picture coding method and the moving picturedecoding method according to each of embodiments.

FIG. 35 shows a configuration for switching between driving frequencies.

FIG. 36 shows steps for identifying video data and switching betweendriving frequencies.

FIG. 37 shows an example of a look-up table in which video datastandards are associated with driving frequencies.

FIG. 38A is a diagram showing an example of a configuration for sharinga module of a signal processing unit.

FIG. 38B is a diagram showing another example of a configuration forsharing a module of the signal processing unit.

DESCRIPTION OF EMBODIMENTS Embodiment 1 (Underlying Knowledge FormingBasis of the Present Disclosure)

The inventors have found that there is the following problem with theimage coding method for coding an image and image decoding method fordecoding an image described in the section of “Background Art”.

In recent years, techniques for use in digital video equipment haveadvanced significantly, so that there are more and more occasions toperform compression coding on video signals (time-series pictures for amoving picture) input from a camcorder or a television tuner to recordthem on recording media such as a Digital Versatile Disc (DVD) or a harddisk or to distribute them through a network.

Such an image coding method for video coding generally includes thefollowing steps: generating a prediction image of a current image to becoded; calculating a difference image between the prediction image andthe current image; transforming the difference image from a picturedomain into a frequency domain to obtain frequency coefficients(coefficients); and arithmetic-coding of the frequency coefficients.

According to a standard for image coding referred to as H.264/AVC orMPEG-4 AVC (see Non Patent Literature 1), a current block to be coded isdivided into one or more current blocks to be coded. Each of the currentblocks to be coded is further divided into one or more transform blocks.The above-described obtaining of frequency coefficients is performed oneach of the transform block. Furthermore, a parameter arithmeticallycoded in the above-described arithmetic-coding includes a flagindicating whether or not the transform block has a non-zero frequencycoefficient. The flag is referred to as a Coded Block Pattern (CBP) inH.264/AVC, and a Coded Block Flag (CBF) in HEVC.

In decoding of an image, steps such as inverse frequency transform areperformed on a transform block which has a flag having a value of 1.

However, there is a problem with the conventional technique that a flagneeds to be coded for each transform block so that the amount of codesis large.

In order to solve the problem, provided is an image coding methodaccording to an aspect of the present disclosure which is an imagecoding method of coding an input image including one or more transformblocks each having a luma component and a chroma component, the lumacomponent being to be processed on the basis of a luma block whichbelongs to a current one of the one or more transform blocks and has thesame size as a size of the current transform block, the chroma componentbeing to be processed on the basis of a chroma block which belongs tothe current one of the one or more transform blocks and has a sizesmaller than the size of the luma block, and the image coding methodincluding: deriving coefficients of the luma component by performingtransform on the luma component and deriving coefficients of the chromacomponent by performing transform on the chroma component; and codingthe coefficients of the luma component and the coefficients of thechroma component, wherein in the deriving, when the size of the currenttransform block is a predetermined first minimum size, the coefficientsof the chroma component are derived by performing the transform on thechroma component on the basis of a block resulting from binding aplurality of the chroma blocks, the resulting block having the same sizeas the size of the luma block, and in the coding, when the size of thecurrent transform block is the first minimum size, a flag indicatingwhether or not the coefficients of the chroma component include anon-zero coefficient is not coded, and when the size of the currenttransform block is a size other than the first minimum size, the flag iscoded.

In the image coding method in this configuration, when a block of chromacomponents is smaller than a block of a luma component, when a transformblock has the first minimum size, blocks of a chroma component, which issmaller than a block of a luma component, are bound and processed on thebasis of a block having the same size as the block of the lumacomponent. This makes it no longer necessary to include processingcircuitry, a software module, or the like for coding of blocks on thebasis of a unit having a size smaller than the first minimum size.

Furthermore, in the image coding method in this configuration, coding ofchroma components CBF_Cb and CBF_Cr is not performed on transform blockshaving the first minimum size. In the image coding method in thisconfiguration, CBF_Cb and CBF_Cr in the layer one level higher arereferred to. Thus, CBF_Cb and CBF_Cr of transform blocks having thefirst minimum size are not referred to. Accordingly, it is not necessaryto code CBF_Cb or CBF_Cr of transform blocks having the first minimumsize, so that coding efficiency can be increased by omitting coding ofCBF_Cb and CBF_Cr.

For example, the transform blocks may be blocks resulting from splittinga coding block in quadtree structure, second minimum size of the codingblock may be limited to a size larger than the first minimum size, andin the coding, the flag may be coded when (1) the size of the currenttransform block is larger than the first minimum size and (2) thecurrent transform block belongs to a layer at a highest level in thequadtree structure, or when the flag has a value of 1 in a layer onelevel higher in the quadtree structure than a layer to which the currenttransform block belongs.In order to solve the problem, provided is an image decoding methodaccording to an aspect of the present disclosure which is an imagedecoding method of decoding, from a coded bitstream, an image includingone or more transform blocks each having a luma component and a chromacomponent, the luma component being to be processed on the basis of aluma block which belongs to a current one of the one or more transformblocks and has the same size as a size of the current transform block,the chroma component being to be processed on the basis of a chromablock which belongs to a current one of the one or more transform blocksand has a size smaller than a size of the luma block, and the imagedecoding method including: decoding coefficients of the luma componentand coefficients of the chroma component which are coded and included inthe coded bitstream; and deriving the luma component by performingtransform on the coefficients of the luma component and deriving thechroma component by performing transform on the coefficients of thechroma component, wherein in the deriving, when the size of the currenttransform block is a predetermined first minimum size, the coefficientsof the chroma component are derived by performing the transform on thechroma component on the basis of a block resulting from binding aplurality of the chroma blocks, the resulting block having the same sizeas the size of the luma block, and in the decoding, when the size of thecurrent transform block is a size other than the first minimum size, aflag indicating whether or not the coefficients of the chroma componentinclude a non-zero coefficient is decoded.

In the image decoding method in this configuration, when a transformblock has the first minimum size, blocks of a chroma component, which issmaller than a block of a luma component, are bound and processed on thebasis of a block having the same size as the block of the lumacomponent. This makes it no longer necessary to include processingcircuitry, a software module, or the like for decoding of blocks on thebasis of a unit having a size smaller than the first minimum size.

Furthermore, in the image decoding method in this configuration,decoding of chroma components CBF_Cb and CBF_Cr are not performed ontransform blocks having the first minimum size. In the image decodingmethod in this configuration, CBF_Cb and CBF_Cr in the layer one levelhigher are referred to. Thus, CBF_Cb and CBF_Cr of transform blockshaving the first minimum size are not referred to. Accordingly, it isnot necessary to code CBF_Cb or CBF_Cr of transform blocks having thefirst minimum size, so that even when a bitstream includes any of theflags, coding efficiency can be increased by omitting coding of CBF_Cband CBF_Cr.

For example, the transform blocks may be blocks resulting from splittinga decoding block in quadtree structure, a second minimum size of thedecoded block may be limited to a size larger than the first minimumsize, and in the decoding, the flag may be decoded when (1) the size ofthe current transform block is larger than the first minimum size and(2) the current transform block belongs to a layer at a higher level inthe quadtree structure, or when the flag has a value of 1 in a layer onelevel higher in the quadtree structure than a layer to which the currenttransform block belongs.

In order to solve the problem, provided is an image coding apparatusaccording to an aspect of the present disclosure which is an imagecoding apparatus which transforms a chroma component and a lumacomponent of an input image and includes: processing circuitry; andstorage accessible from the processing circuitry, the input imageincluding one or more transform blocks each having a luma component anda chroma component, the luma component being to be processed on thebasis of a luma block which is belongs to a current one of the one ormore transform blocks and has the same size as a size of the currenttransform block, the chroma component being to be processed on the basisof a chroma block which is in a current one of the one or more transformblocks and has a size smaller than the size of the luma block, and theprocessing circuitry being configured to derive coefficients of the lumacomponent by performing transform on the luma component and derivingcoefficients of the chroma component by performing transform on thechroma component, and code the coefficients of the luma component andthe coefficients of the chroma component, wherein when the size of thecurrent transform block is a predetermined first minimum size, theprocessing circuitry is configured to derive the coefficients of thechroma component by performing the transform on the chroma component onthe basis of a block resulting from binding a plurality of the chromablocks, the resulting block having the same size as the size of the lumablock, and when the size of the current transform block is the firstminimum size, the processing circuitry is configured not to code a flagindicating whether or not the coefficients of the chroma componentinclude a non-zero coefficient, and when the size of the currenttransform block is a size other than the first minimum size, theprocessing circuitry is configured to code the flag.

In order to solve the problem, provided is an image decoding apparatusaccording to an aspect of the present disclosure which is an imagedecoding apparatus which decodes an image from a coded bitstream andincludes: processing circuitry; and storage accessible from theprocessing circuitry, the image including one or more transform blockseach having a luma component and a chroma component, the luma componentbeing to be processed on the basis of a luma block which belongs to acurrent one of the one or more transform blocks and has the same size asa size of the current transform block, the chroma component being to beprocessed on the basis of a chroma block which is in a current one ofthe one or more transform blocks and has a size smaller than the size ofthe luma block, and the processing circuitry being configured to decodecoefficients of the luma component and coefficients of the chromacomponent which are coded and included in the coded bitstream, andderive the luma component by performing transform on the coefficients ofthe luma component and deriving the chroma component by performingtransform on the coefficients of the chroma component, wherein when thesize of the current transform block is a predetermined first minimumsize, the processing circuitry is configured to derive the coefficientsof the chroma component by performing the transform on the chromacomponent on the basis of a block resulting from binding a plurality ofthe chroma blocks, the resulting block having the same size as the sizeof the luma block, and when the size of the current transform block is asize other than the first minimum size, the processing circuitry isconfigured to decode a flag indicating whether or not the coefficientsof the chroma component include a non-zero coefficient.

In order to solve the problem, an image coding and decoding apparatusaccording to an aspect of the present disclosure includes the imagecoding apparatus and the image decoding apparatus.

Hereinafter, embodiments will be concretely described with reference tothe drawings. Each of the embodiments described below is described as ageneral or a concrete example. The numerical values, shapes, materials,structural elements, the arrangement and connection of the structuralelements, steps, the processing order of the steps etc. shown in thefollowing exemplary embodiments are mere examples, and therefore do notlimit the present disclosure. Therefore, among the structural elementsin the following exemplary embodiments, structural elements not recitedin any one of the independent claims are described as arbitrarystructural elements.

In addition, the term “coding” in the following description may be usedto mean “encoding”.

Embodiment 1

An image coding apparatus and an image coding method in Embodiment 1will be described below using FIG. 1 to FIG. 12.

1-1. Overall Configuration

Firstly, an overall configuration of the image coding apparatus inEmbodiment 1 will be described on the basis of FIG. 1. FIG. 1 is a blockdiagram showing an example of a configuration of the image codingapparatus (in part) in Embodiment 1.

The image coding apparatus 100 in Embodiment 1 is an apparatus whichperforms frequency transform on chroma components and a luma componentof an input image. The image coding apparatus 100 splits an input imageinto one or more coding blocks in a tree structure, and splits each ofthe coding blocks into one or more transform blocks in the treestructure. In Embodiment 1, a quadtree structure is used as an exampleof the tree structure.

As shown in FIG. 1, the image coding apparatus 100 includes an LCUsplitting unit 101, a CU split size determination unit 102, a TU splitsize determination unit 103, a CBF_CbCr determination unit 104, aquadtree coding unit 105, and a frame memory 106 (an example of astorage device).

A detailed configuration (operation) of the LCU splitting unit 101, CUsplit size determination unit 102, TU split size determination unit 103,CBF_CbCr determination unit 104, and frame memory 106 will be describedlater in 1-3.

1-2. Configuration of the Quadtree Coding Unit 105

A configuration of the quadtree coding unit 105 will be described belowon the basis of FIG. 2. FIG. 2 is a block diagram showing an exemplaryconfiguration of the quadtree coding unit 105.

As shown in FIG. 2, the quadtree coding unit 105 includes a CU splitflag coding unit 110 and a CU coding unit 120.

The CU coding unit 120 includes a prediction unit 121, a subtractor 122,an adder 123, and a quadtree transform unit 130.

The quadtree transform unit 130 includes a TU split flag coding unit131, a CBF coding unit 132, and a TU coding unit 140.

The TU coding unit 140 includes a transform unit 141, a frequencycoefficient coding unit 142, and an inverse transform unit 143.

A detailed configuration (operation) of each component of the quadtreecoding unit 105 will be described in subsections 1-4 to 1-7 below.

1-3. Overall Operation

Overall operation of the image coding apparatus 100 will be described onthe basis of FIG. 3. FIG. 3 is a flowchart showing an exemplary overalloperation of the image coding apparatus 100.

As shown in FIG. 3, the LCU splitting unit 101 splits an input imageinto, for example, blocks having a size of 64×64 (largest coding units(LCUs)), and outputs the LCUs sequentially to the CU split sizedetermination unit 102, the TU split size determination unit 103, theCBF_CbCr determination unit 104, and the quadtree coding unit 105 (StepS101). Subsequent steps of the processing (S102 to S106) for LCSs are tobe performed on each LCU in each picture (input image), and thus thesteps S102 to S106 are performed on all LCUs in each picture.

The CU split size determination unit 102 splits an LCU into one or morecoding units (CUs) (S102). The size of the CUs is variable, and the CUsmay have different sizes.

FIG. 4 shows an example of splitting of an LCU into one or more CUs. InFIG. 4, the whole block (the block including 1 to 16) is a single LCU.The blocks numbered 1 to 16 in FIG. 4 each represent a CU. The numbersin the blocks represent a coding order. The CU split size determinationunit 102 determines CU split sizes based on features of already codedimages or features of the input image. In Embodiment 1, the minimum sizeof CUs (a second minimum size) is 8 horizontal pixels×8 vertical pixelsand the maximum size thereof is 64 horizontal×64 vertical pixels. CUsmay have a maximum size or a minimum size other than the one above.

The CU split size determination unit 102 determines a value of a CUsplit flag to indicate a method of splitting the CU, and outputs the CUsplit flag to the quadtree coding unit 105. The CU split flag indicateswhether or not the block is to be split.

FIG. 5 shows an example of values of CU split flags corresponding to theLCU shown in FIG. 4. In FIG. 5, the value in each square is the value ofa CU split flag. The CU split flag having a value of 1 indicates thatthe block is to be split into quadrantal blocks, and the CU split flaghaving a value of 0 indicates that the block is not to be split. Each ofthe quadrantal blocks has a CU split flag therein. In other words, ablock is recursively split while the block has a CU split flag having avalue of 1 or while the CU size is larger than 8×8. CU Layer is aparameter indicating a level of splitting (the number of splitting). Thelarger the value of CU Layer is, the smaller the size of CUs is. InEmbodiment 1, the maximum size of CUs is 64×64 and the minimum size is8×8, and thus the value of CU Layer runs from 0 to 3. In FIG. 5, at thelevel where CU Layer has a value of 0, a CU split flag has a value of 1indicating that the block is to be split. At the level where CU Layerhas a value of 1, the CU split flags of the upper-right CU and thelower-left CU in FIG. 5 have a value of 0 indicating that thecorresponding block is not to be split, and the CU split flags of theupper-left CU and the lower-right CU in FIG. 5 have a value of 1indicating that the corresponding block is to be split. At the levelwhere CU Layer has a value of 2, no CU split flag is set for theupper-right CU and the lower-left CU in FIG. 5. Furthermore, at thelevel where CU Layer has a value of 2, the upper-left four blocks andthe lower-right four blocks in FIG. 5 each has a CU split flag having asetting value of 0 or 1. At the level where CU Layer has a value of 3,there are quadrantal blocks resulting from splitting the blocks each ofwhich has a CU split flag having a value of 1 at the level where CULayer has a value of 2. The quadrantal blocks have a CU size of 8×8. TheCU size is the minimum size and the blocks are never to be split. Thus,the CU split flags of the blocks necessarily have a value of 0.Accordingly, CU split flags at the level where CUs have the minimum sizeneed not be coded. Thus, in FIG. 5, the values of the CU split flags atthe level where CU Layer has a value of 3 are denoted by parenthesizedzero, that is, (0). A method of coding a CU split flag will be describedin detail in subsection “1-4. Quadtree coding” below.

The TU split size determination unit 103 splits CUs into one or moretransform units (TUs) (Step 103). The size of the TUs is variable, andthe TUs may have different sizes.

FIG. 6 shows an example of splitting of a LCU shown in FIG. 4 into oneor more TUs. In FIG. 6, each thick-frame square represents a CU, andeach thin-frame square represents a TU. The numbers in TUs represent atransform order. The TU split size determination unit 103 determinessplit sizes based on features of already coded images or features of theinput image. In Embodiment 1, the minimum size of TUs (a first minimumsize) is 4 horizontal pixels×4 vertical pixels, and the maximum sizethereof is 64 horizontal×64 vertical pixels. TUs may have a maximum sizeor a minimum size other than the one above.

The TU split size determination unit 103 determines a value of a TUsplit flag to indicate a method of splitting the TU, and outputs thevalue to the quadtree coding unit 105. The TU split flag indicateswhether or not the block is to be split.

FIG. 7 shows exemplary values of TU split flags in the case where thetwelfth CU in the coding order shown in FIG. 4 is split into TUs in themanner shown in FIG. 6. In FIG. 7, the values in the squares denote thevalues of TU split flags. The TU split flag having a value of 1indicates that the block is to be split into quadrantal blocks, and theTU split flag having a value of 0 indicates that the block is not to besplit. Also the quadrantal blocks each include a TU split flag therein.In other words, blocks are recursively split while a TU split flag has avalue of 1 or while the TU size is larger than 4×4. TU Layer is aparameter indicating a level of splitting (the number of splitting). Thelarger the value of TU Layer is, the smaller the size of TUs is. InEmbodiment 1, in FIG. 7, the maximum size of CUs is 32×32 and theminimum size is 4×4, and thus the value of TU Layer runs from 0 to 3. Inthe example shown in FIG. 7, at the level where TU Layer has a value of3, there are quadrantal blocks resulting from splitting the block whichhas a TU split flag having a value of 1 at the level where TU Layer hasa value of 2. The quadrantal blocks have a TU size of 4×4. The TU sizeis the minimum size and the blocks are never to be split. Thus, the TUsplit flags of the blocks necessarily have a value of 0. Accordingly, TUsplit flags at the level where TUs have the minimum size need not becoded. Thus, the values of the TU split flags at the level where TULayer has a value of 3 in FIG. 7 are denoted by parenthesized zero, thatis, (0). A method of coding a TU split flag will be described in detailin subsection “1-6. Quadtree transform” below.

The blocks at the level where TU Layer has a value of 0 has a size of32×32 in the example shown in FIG. 7 because the CU size is 32×32. Thisholds true also for the block numbered 11 in FIG. 4. Note that since theCUs numbered 2 to 9 in FIG. 4 has a size of 8×8, the blocks at the levelwhere TU Layer has a value of 0 have a size of 8×8. Also note that sincethe CUs numbered 10 and 13 to 16 in FIG. 4 has a size of 16×16, theblocks at the level where TU Layer has a value of 0 have a size of16×16.

The CBF_CbCr determination unit 104 determines CBF_Cb and CBF_Cr of eachTU (S104). CBF_Cb and CBF_Cr are flags which indicate whether or notthere is any frequency coefficient to be coded for chroma components(Cb, Cr). When there is any non-zero coefficient to be coded for Cb andCr in a TU, CBF_Cb and CBF_Cr of the TU is respectively determined tobe 1. When there is no non-zero coefficient to be coded in a TU (thatis, all frequency coefficients of a TU are zero), CBF_Cb and CBF_Cr aredetermined to be 0. The values of CBF_Cb and CBF_Cr are each set basedon frequency coefficients obtained by actually performing frequencytransform on differences from a prediction image from a picture domainto a frequency domain.

Next, the quadtree coding unit 105 performs quadtree coding (S105). Thiswill be described in detail later.

1-4. Operation (Quadtree Coding)

Operation of the quadtree coding unit 105 (details of operation in StepS105 in FIG. 3) will be described below on the basis of FIG. 8. FIG. 8is a flowchart showing an example of steps in processing of quadtreecoding.

For CU Layer having a value smaller than 3 (S111, Yes) in FIG. 5, the CUsplit flag coding unit 110 of the quadtree coding unit 105 codes a CUsplit flag (S112). For CU Layer having a value of 3 (S111, No), the CUsplit flag coding unit 110 sets the CU split flag to have a value of 0without performing coding thereon (S113).

Note that the CU size at the levels where CU Layer has a value smallerthan 3 in FIG. 5 is 16×16 or larger, and that the CU size at the levelwhere CU Layer has a value of 3 is 8×8 or larger. CU Layer never has avalue of four or greater because the CU size of 8×8 is the minimum size.In other words, a CU having a size of 8×8 is never to be split, and thusthe CU split flag coding unit 110 sets a CU split flag to have a valueof 0 without performing coding thereon.

When a CU split flag has a value of 0 (S114, No), the CU coding unit 120performs CU coding (S119). This will be described in detail later. Whena CU split flag has a value of 1 (S114, Yes), the CU coding unit 120splits the block into quadrantal blocks. Then, the CU coding unit 120recursively performs this processing of quadtree coding on each of thequadrantal blocks (S115 to S118).

1-5. Operation (CU Coding)

Operation of the CU coding unit 120 (details of operation in Step S119in FIG. 8) will be described below on the basis of FIG. 9. FIG. 9 is aflowchart showing an example of steps in processing of CU coding.

The prediction unit 121 of the CU coding unit 120 generates a predictionblock from a current CU to be coded (current CU) and a decoded imagestored in the frame memory 106 (S121).

The subtractor 122 generates a difference block from the current CU anda prediction block generated by the prediction unit 121 (S122).

The quadtree transform unit 130 performs frequency transform, coding,and inverse frequency transform on frequency coefficients for thedifference block generated by the subtractor 122 (S123). The differenceblock is reconstructed through the inverse frequency transform (areconstruction difference block is generated). This will be described indetail later.

The adder 123 generates a reconstruction block by adding thereconstruction difference block reconstructed by the quadtree transformunit 130 performing the inverse frequency transform and the predictionblock generated by the prediction unit 121, and stores thereconstruction block in the frame memory 106 (S124).

1-6. Operation (Quadtree Transform)

Operation of the quadtree transform unit 130 (details of operation inStep S123 in FIG. 9) will be described below on the basis of FIG. 10.FIG. 10 is a flowchart showing an example of steps in processing ofquadtree transform.

When the sum of the value of CU Layer and the value of TU Layer issmaller than four (S131, Yes), the TU split flag coding unit 131 of thequadtree transform unit 130 codes the TU split flag (S132). When the sumof the value of CU Layer and the value of TU Layer is four (S131, No),the TU split flag coding unit 131 sets the TU split flag to have a valueof 0 without coding the TU split flag (S133).

In this step, the TU split flag coding unit 131 determines whether ornot a TU has a size of 4×4 for TU Layer of the current level. When a TUhas a size of 4×4, coding of a TU split flag is not performed. Theminimum size of TUs is 4×4, and thus a TU having a size of 4×4 is neverto be split. Thus, when the size of TUs is 4×4, the TU split flag codingunit 131 sets a TU split flag to have a value of 0 without performingcoding on the TU split flag.

The CU size can be determined from the value of CU Layer. However, theTU size cannot be determined only from the value of TU Layer. The valueof CU Layer is also used to determine the TU size. Since the TU size ofTU Layer depends on the CU size of CU Layer at a level where TU Layerhas a value of 0, the TU size can be determined by adding the value ofCU Layer and the value of TU Layer. When the sum of the value of CULayer and the value of TU Layer is zero, the TU size is 64×64. When thesum is four, the TU size is 4×4. Since the TU size of 4×4 is the minimumsize, the sum is always below five.

When the sum of the value of CU Layer and the value of TU Layer issmaller than four (that is, when the TU size for TU Layer at the currentlevel is larger than 4×4) (S134, Yes), the CBF coding unit 132 codesCBF_Cb and CBF_Cr (S135 to S142). When the sum of the value of CU Layerand the value of TU Layer is four (that is, when the TU size for TULayer at the current level is 4×4), the CBF coding unit 132 does notcode CBF_Cb or CBF_Cr. The reason for not coding CBF_Cb or CBF_Cr whenthe TU size of TU Layer at the current level is 4×4 will be described inthe following subsection in which processing flow of TU coding will bedescribed.

When TU Layer has a value of 0 (S135, Yes) or when TU Layer does nothave a value of 0 and CBF_Cb for TU Layer one level higher has a valueof 1 (S135, No; and S136, Yes), the CBF coding unit 132 codes CBF_Cb(S137). When TU Layer does not have a value of 0 and CBF_Cb for TU Layerone level higher does not have a value of 1 (S135, No; and S136, No),the CBF coding unit 132 sets CBF_Cb to have a value of 0 (S138).

Furthermore, when TU Layer has a value of 0 (S139, Yes) or when TU Layerdoes not have a value of 0 and CBF_Cr for TU Layer one level higher hasa value of 1 (S139, No; and S140, Yes), the CBF coding unit 132 codesCBF_Cr (S141). When TU Layer does not have a value of 0 and CBF_Cb forTU Layer one level higher does not have a value of 1 (S139, No; andS140, No), the CBF coding unit 132 sets CBF_Cr to have a value of 0(S142).

In other words, the CBF coding unit 132 codes CBF_Cb (or CBF_Cr) onlywhen TU Layer has a value of 0 (TU Layer at the highest level) or whenCBF_Cb (or CBF_Cr) for TU Layer one level higher has a value of 1. Whenthe coding is not performed, CBF_Cb (or CBF_Cr) is set to have a valueof 0, and then the processing proceeds to the following step. This meansthat coding of CBF is performed on a per layer basis. When CBF of ablock for TU Layer one level higher has a value of 0, CBF of each of thequadrantal blocks for TU Layer at the current level is to have a valueof 0.

When a TU split flag has a value of 0 (S143, No), the TU coding unit 140performs TU coding (S148). This will be described in detail later.

When a TU split flag has a value of 1 (S143, Yes), the TU coding unit140 splits the block into quadrantal blocks. Then, the TU coding unit140 recursively performs this processing of quadtree transform on eachof the quadrantal blocks (S144 to S147).

1-7. Operation (TU Coding)

Operation of the TU coding unit 140 (details of operation in Step S148in FIG. 10) will be described below on the basis of FIG. 11. FIG. 11 isa flowchart showing an example of steps in processing of TU coding (partof the image coding method).

First, the TU coding unit 140 performs TU coding on a luma (brightness)component of an image (S151 to S153).

More specifically, the transform unit 141 of the TU coding unit 140performs frequency transform on luma pixels of a TU to transform a lumacomponent from a picture domain to a frequency domain to obtainfrequency coefficients (S151). Furthermore, the frequency coefficientcoding unit 142 codes the frequency coefficients resulting from thetransforming by the transform unit 141 and outputs a code sequence(S152). The inverse transform unit 143 performs inverse frequencytransform on the frequency coefficients resulting from the transformingby the transform unit 141 to transform the frequency coefficients from afrequency domain to a picture domain (S153).

Next, the TU coding unit 140 performs TU coding on chroma (colordifference) components of the image (S154 to S171).

More specifically, when the sum of the value of CU Layer and the valueof TU Layer is smaller than four (or when the TU size is larger than4×4) (S154, Yes), the transform unit 141 moves on to Step S155.

When CBF_Cb has a value of 1 in Step S155 (S155, Yes), the transformunit 141 performs frequency transform on Cb component pixels in the TU(S156). The frequency coefficient coding unit 142 codes the frequencycoefficients resulting from the transforming by the transform unit 141and outputs a code sequence (S157). The inverse transform unit 143performs inverse frequency transform on the frequency coefficientsresulting from the transforming by the transform unit 141 (S158), andthen moves on to Step S159.

When CBF_Cb has a value of 0 in Step S155, the TU includes no non-zerocoefficient to be coded. Thus, the transform unit 141 (S155, No) moveson to Step S159.

When CBF_Cr 1 has a value of 1 in Step S159 (S159, Yes), the transformunit 141 performs frequency transform on Cr component pixels in the TU(S160). The frequency coefficient coding unit 142 codes the frequencycoefficients resulting from the transforming by the transform unit 141and outputs a code sequence (S161). The inverse transform unit 143performs inverse frequency transform on the frequency coefficientsresulting from the transforming by the transform unit 141 (S162). Assumethat image is in 4:2:0 format, and therefore the number of Cb pixels andthe number of Cr pixels are each one-fourth the number of luma pixels.

When CBF_Cr has a value of 0 in Step S159 (S159, No), the TU includes nonon-zero coefficient to be coded. Thus, the transform unit 141 ends theprocessing on Cr.

When it is determined that the sum of the value of CU Layer and thevalue of TU Layer is four (or when the TU size is 4×4) in Step S154(S154, No), the TU coding unit 140 performs frequency transform andcoding (S164 to S171) only when the lower-right one of quadrantal blocksis the current TU (S163, Yes).

Hereinafter, this processing will be concretely described with referenceto FIG. 6. In FIG. 6, the twenty-fourth to twenty-seventh TUs intransform order have a size of 4×4. When any of the twenty-fourth totwenty-sixth TUs in transform order is the current TU to be processed,the TU coding unit 140 does not perform frequency transform or coding onCb or Cr. Instead, the TU coding unit 140 processes Cb of thetwenty-fourth to twenty-seventh TUs in transform order at once when thetwenty-seventh TU is the current TU to be processed. The TU coding unit140 processes Cr in the same manner. In other words, the TU coding unit140 binds Cb pixels in the twenty-fourth to twenty-seventh TUs intransform order to form a 4×4-pixel block when the twenty-seventh TU isthe current TU to be processed, and performs frequency transform andcoding on the 4×4-pixel block. The TU coding unit 140 performs frequencytransform and coding on Cr pixels in the same manner.

This is because when Cb or Cr of a TU having a size of 4×4 is processedin the same manner as a luma component, frequency transform is performedon each 2×2-pixel block. When the image coding apparatus 100 isimplemented as a circuit such as an LSI, the image coding apparatus 100needs to include not only a circuit for 4×4-pixel frequency transformbut also a circuit for 2×2-pixel frequency transform to perform thefrequency transform on each 2×2-pixel block. When the image codingapparatus is implemented as a software program, it is necessary for thesoftware program to include a module for 2×2-pixel frequency transformin addition to a module for 4×4-pixel frequency transform. Thus, suchnecessity of frequency transform of each 2×2-pixel block is eliminatedby binding quadrantal blocks.

In other words, in Embodiment 1, quadrantal blocks are bound so that thefrequency transform and coding on each chroma component are performed onpixels as few as pixels of the luma component on which frequencytransform and coding are performed.

Since frequency transform and so on are performed on bound quadrantalblocks, the TU coding unit 140 determines, with reference to CBF_Cb forTU Layer one level higher, whether or not to perform the frequencytransform and so on (S164). In an example shown in FIG. 6 and FIG. 7,the TU coding unit 140 refers to CBF_Cb for TU Layer having a value of 2in order to make the determination for the twenty-fourth totwenty-seventh TUs in transform order.

FIG. 12 shows an example of CBF_Cb corresponding to a TU in FIG. 7. Inthe case of the twenty-fourth to twenty-seventh TUs in transform ordershown in FIG. 6, CBF_Cb for TU Layer having a value of 2 has a valueof 1. In this case, the TU coding unit 140 determines to performfrequency transform and so on (S164, Yes).

When the TU coding unit 140 determines to perform frequency transformand so on in Step S164, the transform unit 141 performs frequencytransform on Cb (S165), the frequency coefficient coding unit 142 codesfrequency coefficients (S166), and the inverse transform unit 143performs inverse frequency transform (S167).

Similarly, the TU coding unit 140 determines, with reference to CBF_Crfor TU Layer one level higher, whether or not to perform frequencytransform and so on (S168). When the TU coding unit 140 determines toperform frequency transform and so on in Step S168, the transform unit141 performs frequency transform on Cr (S169), the frequency coefficientcoding unit 142 codes frequency coefficients (S170), and the inversetransform unit 143 performs inverse frequency transform (S171).

Note that in Embodiment 1, since the TU coding unit 140 makes thedetermination with reference to CBF_Cb or CBF_Cr for TU Layer one levelhigher, the TU coding unit 140 never refers to CBF_Cb or CBF_Cr for TULayer at a lower level where the TU size is 4×4. Thus, in quadtreetransform shown in FIG. 10, CBF_Cb and CBF_Cr are not coded when the sumof the value of CU Layer and the value of TU Layer is four (or when theTU size of TU Layer at the current level is 4×4) (S134, No).

1-8. Effects

As described above, in Embodiment 1, CBF_Cb is coded only when CBF_Cbfor TU Layer one level higher has a value of 1, and CBF_Cr is coded onlywhen CBF_Cr for TU Layer one level higher has a value of 1. Thisconfiguration contributes to reduction in the amount of codes andcomputational complexity. In other words, when CBF_Cb for TU Layer at acertain level has a value of 0, CBF_Cb for TU Layer at lower levels neednot be coded however small a TU of TU Layer at the lower levels is splitinto. The same applies to CBF_Cr. As a result, the amount of codes andcomputational complexity are reduced.

Furthermore, in Embodiment 1, when the TU size is 4×4, frequencytransform of Cb and Cr is performed on the basis of bound quadrantalblocks. In other words, coding of CBF_Cb or CBF_Cr is not performed forTU Layer at a level where the TU size is 4×4. This enables reduction incircuit size of an arithmetic unit and the amount of codes. Morespecifically, frequency transform of chroma (Cb and Cr) components isalso performed on the basis of bound quadrantal blocks so that theminimum size for the frequency transform can be 4×4. The image codingapparatus 100 thus no longer needs to include a circuit for 2×2-pixelfrequency transform, so that the circuit size can be reduced.Furthermore, CBF_Cb or CBF_Cr for TU Layer at a level where the TU sizeis 4×4 is not necessary when four quadrantal blocks are bound asdescribed above. Thus, the amount of codes can be reduced.

Furthermore, CBF_Cb and CBF_Cr are coded for TU Layer at the highestlevel, but CBF_Cb or CBF_Cr is not coded for TU Layer at a level wherethe TU size is 4×4 as described above. This conflict can be avoided bysetting the minimum size of CUs larger than 4×4 so that TUs are alwayslarger than 4×4 for TU Layer at the highest level. In other words,coding of CBF_Cb or CBF_Cr is performed upon the satisfaction of thefollowing two conditions:

(1) TU Layer is at a level where TUs have a size larger than the minimumsize; and(2) CBF_Cb or CBF_Cr for TU Layer at the highest level or for TU Layerone level higher has a value of 1.

In Embodiment 1, the minimum size of CUs is limited to 8×8 so that thecondition (1) is satisfied.

In Embodiment 1, the TU size of TU Layer, which is determined from thesum of the value of CU Layer and the value of TU Layer, may bedetermined using any other method of determining a TU size. For example,the TU size may be determined by using another parameter or by countingthe number of recursive executions of quadtree coding or quadtreetransform.

Furthermore, although CBF is not used for a luma component in theforegoing description, whether or not to perform coding (includingfrequency transform and so on) may be determined using CBF as in themethod for Cb and Cr components.

Furthermore, the above-described processing in which the TU split flagis not coded and is set to have a value of 0 (no split) when the TU sizeis the minimum size, is given as a non-limiting example. For example, incontrast to the foregoing description, the TU split flag may beprocessed in a manner such that when the TU size is larger than apredetermined maximum TU size, the split flag is not coded and is set tohave, for example, a value of 1 indicating the TU is to be split.

Furthermore, the above-described processing in which Cb or Cr isprocessed on the basis of bound quadrantal blocks to omit frequencytransform for 2×2 blocks when the TU size is 4×4, is given as anon-limiting example. For example, when the minimum TU size is set to8×8, Cb or Cr may be processed on the basis of four bound quadrantalblocks to eliminate necessity of performing frequency transform for 4×4blocks when the TU size is 8×8. Conditions for binding blocks for theprocessing may be adaptively set depending on a minimum TU size. Inother words, a condition may be set such that quadrantal blocks arebound when the TU size is larger than 8×8. It is also possible that TUshaving a minimum size, which is variable, are bound and processed.

Furthermore, the above-described processing in which frequency transformis performed in the quadtree coding unit 105 (1-7, Step S151 in FIG.11), is given as a non-limiting example. For example, it is alsopossible to use a configuration in which a result of frequency transformperformed in determining CBF_Cr and CBF_Cb by the CBF_CbCr determinationunit 104 (1-3, Step S104 in FIG. 3) is stored in memory and is read tobe used in frequency transform performed in coding of frequencycoefficients by the quadtree coding unit 105 (the frequency coefficientcoding unit 142, Step S152 in FIG. 11).

Furthermore, the above-described processing in which determining a CUsplitting size (CU split size determination unit 102) and a TU splittingsize (TU split size determination unit 103) using features of an alreadycoded image or features of input image, is given as a non-limitingexample. For example, a CU split size and a TU split size may bedetermined from the amount of codes based on frequency coefficientsactually obtained as a result of frequency transform of a differencefrom a prediction image. Furthermore, the prediction information,difference blocks, and result of the frequency transform may be alsoused by the CBF_CbCr determination unit 104 or the quadtree coding unit105.

Furthermore, the above-described processing in which the inversetransform unit 143 generates a reconstruction block by adding areconstructed difference block and a prediction block separately fromquadtree transform (1-6), is given as a non-limiting example. Generationof a reconstruction block and quadtree transform may be performedtogether. For example, a reconstruction block may be generated by addinga reconstructed difference block to a prediction block immediately afterinverse frequency transform performed in quadtree transform.

The applicable sizes of an LCU include, but are not limited to 64×64,32×32, 128×128, and a further smaller size or a further larger size.

The maximum CU size is not limited to 64×64, and the minimum CU size isnot limited to 8×8. A CU may have any size smaller or larger than thesesizes, as long as it is larger than the minimum TU size (for example,4×4). Optionally, the size of a CU may be varied depending on the sizeof an LCU.

The maximum TU size is not limited to 64×64, and the minimum TU size isnot limited to 4×4. A TU may have any size smaller or larger than thesesizes, as long as the minimum CU size is larger than the minimum TU size(for example, 4×4). Optionally, the size of a TU may be varied dependingon the size of an LCU.

Furthermore, the processing in Embodiment 1 may be implemented assoftware. The software may be distributed via download. The software maybe also distributed via recording media such as a CD-ROM on which thesoftware is recorded. This holds true also for other embodiments in thepresent Description.

Embodiment 2

An image decoding apparatus and an image decoding method in Embodiment 2will be described below using FIG. 13 to FIG. 19.

2-1. Overall Configuration

Firstly, an overall configuration of the image decoding apparatus inEmbodiment 2 will be described on the basis of FIG. 13. FIG. 13 is ablock diagram showing an example of a configuration of the imagedecoding apparatus (in part) in Embodiment 2.

As shown in FIG. 13, an image decoding apparatus 200 includes a quadtreedecoding unit 201 and frame memory 202.

2-2. Configuration of the Quadtree Decoding Unit

A configuration of the quadtree decoding unit 201 will be describedbelow on the basis of FIG. 14. FIG. 14 is a block diagram showing anexemplary configuration of the quadtree decoding unit 201.

As shown in FIG. 14, the quadtree decoding unit 201 includes a CU splitflag decoding unit 211 and a CU decoding unit 220.

The CU decoding unit 220 includes an adder 221 and a quadtree transformunit 230.

The quadtree transform unit 230 includes a TU split flag decoding unit231, a CBF decoding unit 232, and a TU decoding unit 240.

The TU decoding unit 240 includes a frequency coefficient decoding unit241 and an inverse transform unit 242.

A detailed configuration (operation) of each component of the quadtreedecoding unit 201 will be described in subsections 2-3 to 2-7 below.

2-3. Overall Operation

Overall operation of the image decoding apparatus 200 will be describedon the basis of FIG. 15. FIG. 15 is a flowchart showing an exemplaryoverall operation of the image decoding apparatus 200.

The quadtree decoding unit 201 performs quadtree decoding on a codedsequence as shown in FIG. 15 (Step 201). This will be described indetail later. This processing is performed on each LCU in each picture,and therefore these steps are performed by the repetition of the numberof the LCUs in the picture (S202). In Embodiment 2, the LCU has a sizeof 64×64.

2-4. Operation (Quadtree Decoding)

Operation of the quadtree decoding unit 201 (details of operation inStep S201 in FIG. 15) will be described below on the basis of FIG. 16.FIG. 16 is a flowchart showing an example of steps in processing ofquadtree decoding. Assume that in the following description, the sameconfigurations of LCUs, CUs, and TUs as those in Embodiment 1 (FIGS. 4,6, 5, 7, and 12) are used as an example.

For CU Layer having a value smaller than 3 (S211, Yes), the CU splitflag decoding unit 211 of the quadtree coding unit 201 decodes a CUsplit flag (S212). For CU Layer having a value of 3 (S211, No), thequadtree decoding unit 201 sets the CU split flag to have a value of 0without performing decoding thereon (S213).

As shown in FIG. 5, the CU size at the levels where CU Layer has a valuesmaller than 3 is 16×16 or larger, and the CU size at the level where CULayer has a value of 3 is 8×8 or larger. CU Layer never has a value of 4or greater because the CU size of 8×8 is the minimum size. In otherwords, a CU having a size of 8×8 is never to be split, and thus the CUsplit flag decoding unit 211 sets a CU split flag to have a value of 0without performing decoding thereon.

When a CU split flag has a value of 0 (S214, No), the CU decoding unit220 performs CU decoding (S219). This will be described in detail later.When a CU split flag has a value of 1 (S214, Yes), the CU decoding unit220 splits the block into quadrantal blocks. Then, the CU decoding unit220 recursively performs this processing of quadtree decoding on each ofthe quadrantal blocks (S215 to S218).

2-5. Operation (CU Decoding)

Operation of the CU decoding unit 220 (details of operation in Step S219in FIG. 16) will be described below on the basis of FIG. 17. FIG. 17 isa flowchart showing an example of steps in processing of CU decoding.

The quadtree transform unit 230 performs quadtree transform (S221). Inthe quadtree transform, the TU decoding unit 240 performs decoding andinverse frequency transform on frequency coefficients. This will bedescribed in detail later.

The adder 221 generates a decoded block by adding a difference blockreconstructed by the quadtree transform unit 230 performing the inversefrequency transform and a prediction block generated from a decodedimage stored in the frame memory 202, and stores the decoded block inthe frame memory 202 (S222). Although not shown, the generating of aprediction block may be performed by a prediction unit provided betweenthe frame memory 202 and the adder 221.

2-6. Operation (Quadtree Transform)

Operation of the quadtree transform unit 230 (details of operation inStep S221 in FIG. 17) will be described below on the basis of FIG. 18.FIG. 18 is a flowchart showing an example of steps in processing ofquadtree transform.

When the sum of the value of CU Layer and the value of TU Layer issmaller than four (S231, Yes), the TU split flag decoding unit 231 ofthe quadtree transform unit 230 decodes the TU split flag (S232). Whenthe sum of the value of CU Layer and the value of TU Layer is four(S231, No), the TU split flag decoding unit 231 sets the TU split flagto have a value of 0 without decoding the TU split flag (S233).

In this step, the TU split flag decoding unit 231 determines whether ornot a TU has a size of 4×4 for TU Layer at the current level. When a TUhas a size of 4×4, decoding of a TU split flag is skipped. The minimumsize of TUs is 4×4, and thus a TU having a size of 4×4 is never to besplit. Thus, when the size of a TU is 4×4, the TU split flag decodingunit 231 sets a TU split flag to have a value of 0 without performingdecoding on the TU split flag.

The CU size can be determined from the value of CU Layer. However, theTU size cannot be determined only from the value of TU Layer. The valueof CU Layer is also necessary to determine the TU size. Since the TUsize of TU Layer depends on the CU size of CU Layer at a level where TULayer has a value of 0, the TU size can be determined by adding thevalue of CU Layer and the value of TU Layer. When the sum of the valueof CU Layer and the value of TU Layer is zero, the TU size is 64×64.When the sum is four, the TU size is 4×4. Since the TU size of 4×4 isthe minimum size, the sum is always below five.

When the sum of the value of CU Layer and the value of TU Layer issmaller than four (that is, when the TU size of the current TU Layer islarger than 4×4) (S234, Yes), the CBF decoding unit 232 decodes CBF_Cband CBF_Cr (S235 to S242). When the sum of the value of CU Layer and thevalue of TU Layer is four (that is, when the TU size of TU Layer at thecurrent level is 4×4) (S234, No), the CBF decoding unit 232 does notdecode CBF_Cb or CBF_Cr. The reason for not decoding CBF_Cb or CBF_Crwhen the TU size is 4×4 will be described in the following subsection inwhich processing flow of TU decoding will be described.

When TU Layer has a value of 0 (S235, Yes) or when TU Layer does nothave a value of 0 and CBF_Cb for TU Layer one level higher has a valueof 1 (S235, No; and S236, Yes), the CBF decoding unit 232 decodes CBF_Cb(S237). When TU Layer does not have a value of 0 and CBF_Cb for TU Layerone level higher does not have a value of 1 (S235, No; and S236, No),the CBF decoding unit 232 sets CBF_Cb to have a value of 0 (S238).

Furthermore, when TU Layer has a value of 0 (S239, Yes) or when TU Layerdoes not have a value of 0 and CBF_Cr for TU Layer one level higher hasa value of 1 (S239, No; and S240, Yes), the CBF decoding unit 232decodes CBF_Cr (S241). When TU Layer does not have a value of 0 andCBF_Cb for TU Layer one level higher does not have a value of 1 (S239,No; and S240, No), the CBF decoding unit 232 sets CBF_Cr to have a valueof 0 (S242).

In other words, the CBF decoding unit 232 decodes CBF_Cb (or CBF_Cr)only when TU Layer has a value of 0 (TU Layer at the highest level) orwhen CBF_Cb (or CBF_Cr) of TU Layer one level higher has a value of 1.When the decoding is not performed, CBF_Cb (or CBF_Cr) is set to have avalue of 0, and then the processing proceeds to the following step. Thismeans that decoding of CBF is performed on a per layer basis. When CBFof a block of TU Layer one level higher has a value of 0, CBF of each ofthe quadrantal blocks of TU Layer at the current level is to have avalue of 0.

When a TU split flag has a value of 0 (S243, No), the TU decoding unit240 performs TU decoding (S248). This will be described in detail later.

When a TU split flag has a value of 1 (S243, Yes), the TU decoding unit240 splits the block into quadrantal blocks. Then, the TU decoding unit240 recursively performs this processing of quadtree transform on eachof the quadrantal blocks (S244 to S247).

2-7. Operation (TU Decoding)

Operation of the TU decoding unit 240 (details of operation in Step S248in FIG. 18) will be described below on the basis of FIG. 19. FIG. 19 isa flowchart showing an example of steps in processing of TU decoding(part of the image decoding method).

First, the TU decoding unit 240 performs TU decoding on a luma(brightness) component of an image (S251 to S252).

More specifically, the frequency coefficient decoding unit 241 of the TUdecoding unit 240 decodes frequency coefficients of a luma component ina TU (S251). Furthermore, the inverse transform unit 242 of the TUdecoding unit 240 performs inverse transform on the decoded frequencycoefficients (S252).

Next, the TU decoding unit 240 performs TU decoding on chroma (colordifference) components of the image (S253 to S266).

More specifically, when the sum of the value of CU Layer and the valueof TU Layer is smaller than four (or when the TU size is larger than4×4) (S253, Yes), the frequency coefficient decoding unit 241 moves onto Step S254.

When CBF_Cb has a value of 1 in Step S254 (S254, Yes), the frequencycoefficient decoding unit 241 decodes frequency coefficients a of Cbcomponent of the TU (S255). The inverse transform unit 242 performsinverse frequency transform on the decoded frequency coefficients(S256).

When CBF_Cr has a value of 1 in Step S254 (S257, Yes), the frequencycoefficient decoding unit 241 decodes frequency coefficients of a Crcomponent of the TU (S258). The inverse transform unit 242 performsinverse frequency transform on the decoded frequency coefficients(S259). Assume that image is in 4:2:0 format, and therefore the numberof Cb pixels and the number of Cr pixels are each one-fourth the numberof luma pixels.

When it is determined that the sum of the value of CU Layer and thevalue of TU Layer is four (or when the TU size is 4×4) in Step S253(S253, No), the TU decoding unit 240 performs decoding and inversefrequency transform (S261 to S266) only when the lower-right block ofquadrantal blocks is the current TU (S260, Yes). Quadrantal blocks arebound so that the decoding and inverse frequency transform on eachchroma component are performed on pixels as few as pixels of the lumacomponent on which decoding and inverse frequency transform areperformed.

Hereinafter, this processing will be concretely described with referenceto FIG. 6. In FIG. 6, the twenty-fourth to twenty-seventh TUs intransform order have a size of 4×4. When the twenty-fourth totwenty-sixth TUs in transform order are the current TU to be processed,the TU decoding unit 240 does not perform decoding or inverse frequencytransform on Cb or Cr. Instead, the TU decoding unit 240 processes Cb ofthe twenty-fourth to twenty-seventh TUs in transform order at once whenthe twenty-seventh TU is the current TU to be processed. The TU decodingunit 240 processes Cr in the same manner. In other words, the TUdecoding unit 240 binds Cb pixels of the twenty-fourth to twenty-seventhTUs in transform order to form a block when the twenty-seventh TU is thecurrent TU to be processed, and reconstruct a difference block for theblock. The TU decoding unit 240 reconstructs a difference block for Crpixels in the same manner.

This is because when a Cb component or a Cr component in a TU having asize of 4×4 are processed in the same manner as a luma component,inverse frequency transform is to be performed on each 2×2 pixel block.When inverse frequency transform is to be performed on each 2×2 pixelblock, a circuit or a software module for 2×2-pixel frequency transformis necessary in addition to a circuit or a software module for 4×4-pixelfrequency transform. Thus, such necessity of frequency transform of each2×2-pixel block is eliminated by binding quadrantal blocks.

In other words, in Embodiment 2, the inverse frequency transform anddecoding on chroma components are performed on the basis of quadrantalblocks bound to be as few as blocks on the basis of which processing ofa luma component is performed.

Since inverse frequency transform and so on are performed on blocks ofbound quadrantal pixels, the TU decoding unit 240 determines, withreference to CBF_Cb for TU Layer one level higher, whether or not toperform the inverse frequency transform and so on (S261). In an exampleshown in FIG. 6 and FIG. 7, the TU decoding unit 240 refers to CBF_Cbfor TU Layer having a value of 2 in order to make the determination forthe twenty-fourth to twenty-seventh TUs in transform order.

The processing will be described below using FIG. 12 as an example. Inthe case of the twenty-fourth to twenty-seventh TUs in transform ordershown in FIG. 6, CBF_Cb for TU Layer having a value of 2 has a valueof 1. In this case, the TU decoding unit 240 determines to performinverse frequency transform and so on (S261, Yes).

When the TU decoding unit 240 determines to perform inverse frequencytransform and so on in Step S261, the frequency coefficient decodingunit 241 performs decoding of frequency coefficients on Cb (S262), andthe inverse transform unit 242 performs inverse frequency transform onthe frequency coefficients (S263).

Similarly, the TU decoding unit 240 determines, with reference to CBF_Crfor TU Layer one level higher, whether or not to perform inversefrequency transform and so on (S264). When the TU decoding unit 240determines to perform inverse frequency transform and so on in StepS264, the frequency coefficient decoding unit 241 performs decoding offrequency coefficients (S265), and the inverse transform unit 242performs inverse frequency transform on the frequency coefficients(S266).

Note that in Embodiment 2, since the TU decoding unit 240 makes thedetermination with reference to CBF_Cb or CBF_Cr for TU Layer one levelhigher when the TU size is 4×4, the TU decoding unit 240 never refers toCBF_Cb or CBF_Cr for TU Layer at a lower level where the TU size is 4×4.Thus, in quadtree transform shown in FIG. 18, CBF_Cb and CBF_Cr are notdecoded when the sum of the value of CU Layer and the value of TU Layeris four (or when the TU size of TU Layer at the current level is 4×4)(S234, No).

2-8. Effects

As described above, in Embodiment 2, CBF_Cb is decoded only when CBF_Cbfor TU Layer one level higher has a value of 1, and CBF_Cr is decodedonly when CBF_Cr for TU Layer one level higher has a value of 1. Thisconfiguration contributes to reduction in the amount of codes andcomputational complexity. In other words, when CBF_Cb for TU Layer at alevel has a value of 0, CBF_Cb for TU Layer at lower levels need not bedecoded however small the TU of TU Layer at the lower level is splitinto. The same applies to CBF_Cr. As a result, the amount of codes andcomputational complexity are reduced.

Furthermore, in Embodiment 2, when the TU size is 4×4, inverse frequencytransform of Cb and Cr is performed on the basis of bound quadrantalblocks. In other words, decoding of CBF_Cb or CBF_Cr is not performedfor TU Layer at a level where the TU size is 4×4. This enables reductionin circuit size of an arithmetic unit and the amount of codes. Morespecifically, inverse frequency transform is performed on the basis ofbound quadrantal blocks so that the minimum size for inverse frequencytransform can be 4×4 in the case of chroma (Cb and Cr) components aswell. The image decoding apparatus 200 thus no longer needs to include acircuit for 2×2-pixel inverse frequency transform, so that the circuitsize can be reduced. Furthermore, as described above, CBF_Cb or CBF_Crfor TU Layer at a level where the TU size is 4×4 is not necessary whenfour quadrantal blocks are bound, so that the amount of codes can bereduced.

Furthermore, CBF_Cb and CBF_Cr are decoded for TU Layer at the highestlevel, but CBF_Cb or CBF_Cr is not decoded for TU Layer at a level wherethe TU size is 4×4 as described above. This conflict can be avoided bysetting the minimum size of CUs larger than 4×4 so that TUs are alwayslarger than 4×4 for TU Layer at the highest level. In other words,decoding of CBF_Cb or CBF_Cr is performed upon the satisfaction of thefollowing two conditions.

(1) TU Layer is at a level where TUs have a size larger than the minimumsize; and(2) CBF_Cb or CBF_Cr for TU Layer at the highest level or for TU Layerone level higher has a value of 1.

In Embodiment 2, the minimum size of CUs is limited to 8×8 so that thecondition (1) is satisfied.

In Embodiment 2, the TU size of TU Layer, which is determined from thesum of the value of CU Layer and the value of TU Layer, may bedetermined using any other method of determining a TU size. For example,the TU size may be determined by using another parameter or by countingthe number of recursive executions of quadtree decoding or quadtreetransform.

Furthermore, although CBF is not used for a luma component in theforegoing description, whether or not to perform decoding (includinginverse frequency transform and so on) may be determined using CBF as inthe method for Cb and Cr components.

Furthermore, the above-described processing in which the TU split flagis not decoded and is set to have a value of 0 (no split) when the TUsize is the minimum size, is given as a non-limiting example. Forexample, in contrast to the foregoing description, the TU split flag maybe processed in a manner such that when the TU size is larger than apredetermined maximum TU size, the split flag is not decoded and is setto have, for example, a value of 1 indicating that the TU is to besplit.

Furthermore, the above-described processing in which Cb or is processedon the basis of bound quadrantal blocks to omit inverse frequencytransform for 2×2 blocks when the TU size is 4×4, is given as anon-limiting example. For example, when the minimum TU size is set to8×8, Cb or Cr may be processed on the basis of four bound quadrantalblocks to eliminate necessity of performing inverse frequency transformfor 4×4 blocks when the TU size is 8×8. Conditions for binding blocksfor the processing may be adaptively set depending on a minimum TU size.In other words, a condition may be set such that quadrantal blocks arebound when the TU size is larger than 8×8. It is also possible that TUshaving a minimum size, which is variable, are bound and processed.

Furthermore, the above-described processing in which the TU decodingunit 240 generates a decoded block by adding a reconstructed differenceblock and a prediction block separately from quadtree transform, isgiven as a non-limiting example. Generation of a decoded block andquadtree transform may be performed together. For example, a decodedblock may be generated by adding a decoded difference block to aprediction block immediately after inverse frequency transform performedin quadtree transform.

The applicable sizes of an LCU include but are not limited to 64×64,32×32, 128×128, and a further smaller size or a further larger size.

The maximum CU size is not limited to 64×64, and the minimum CU size isnot limited to 8×8. The CU may have any size smaller or larger thanthese sizes, as long as it is larger than the minimum TU size (forexample, 4×4). Optionally, the size of a CU may be varied depending onthe size of an LCU.

The maximum TU size is not limited to 64×64, and the minimum TU size isnot limited to 4×4. A TU may have any size smaller or larger than thesesizes, as long as the minimum CU size is larger than the minimum TU size(for example, 4×4). Optionally, the size of a TU may be varied dependingon the size of an LCU.

Generally, each of the functional blocks in the above embodiments can beimplemented using an MPU or memory. Furthermore the processing to beperformed by each of the functional blocks can be implemented assoftware (program) recorded on a recording medium such as a ROM. Thesoftware may be distributed via download or via recording media such asa CD-ROM on which the software is recorded. It is possible as a matterof course to implement each of the functional blocks as hardware(dedicated circuitry).

Furthermore, the processing described in each of the embodiments may beimplemented by integrated processing using a single apparatus (system)or by distributed processing using a plurality of apparatuses. Theprogram may be executed either by a single computer or a plurality ofcomputers. In other words, either integrated processing or distributedprocessing is applicable.

The present invention is not limited to the above-described embodiments.Various variations of the embodiments are possible and are included inthe scope of the present invention.

In the above-described exemplary embodiments, each of the constituentelements may be implemented as a piece of dedicated hardware (processingcircuitry) or implemented by executing a software program appropriatefor the constituent element. The constituent elements may be implementedby a program execution unit such as a CPU or a processor which reads andexecutes a software program recorded on a recording medium such as ahard disk or a semiconductor memory.

Embodiment 3

The processing described in each of embodiments can be simplyimplemented in an independent computer system, by recording, in arecording medium, a program for implementing the configurations of themoving picture coding method (image coding method) and the movingpicture decoding method (image decoding method) described in each ofembodiments. The recording media may be any recording media as long asthe program can be recorded, such as a magnetic disk, an optical disk, amagnetic optical disk, an IC card, and a semiconductor memory.

Hereinafter, the applications to the moving picture coding method (imagecoding method) and the moving picture decoding method (image decodingmethod) described in each of embodiments and systems using thereof willbe described. The system has a feature of having an image coding anddecoding apparatus that includes an image coding apparatus using theimage coding method and an image decoding apparatus using the imagedecoding method. Other configurations in the system can be changed asappropriate depending on the cases.

FIG. 20 illustrates an overall configuration of a content providingsystem ex100 for implementing content distribution services. The areafor providing communication services is divided into cells of desiredsize, and base stations ex106, ex107, ex108, ex109, and ex110 which arefixed wireless stations are placed in each of the cells.

The content providing system ex100 is connected to devices, such as acomputer ex111, a personal digital assistant (PDA) ex112, a cameraex113, a cellular phone ex114 and a game machine ex115, via the Internetex101, an Internet service provider ex102, a telephone network ex104, aswell as the base stations ex106 to ex110, respectively.

However, the configuration of the content providing system ex100 is notlimited to the configuration shown in FIG. 20, and a combination inwhich any of the elements are connected is acceptable. In addition, eachdevice may be directly connected to the telephone network ex104, ratherthan via the base stations ex106 to ex110 which are the fixed wirelessstations. Furthermore, the devices may be interconnected to each othervia a short distance wireless communication and others.

The camera ex113, such as a digital video camera, is capable ofcapturing video. A camera ex116, such as a digital camera, is capable ofcapturing both still images and video. Furthermore, the cellular phoneex114 may be the one that meets any of the standards such as GlobalSystem for Mobile Communications (GSM) (registered trademark), CodeDivision Multiple Access (CDMA), Wideband-Code Division Multiple Access(W-CDMA), Long Term Evolution (LTE), and High Speed Packet Access(HSPA). Alternatively, the cellular phone ex114 may be a PersonalHandyphone System (PHS).

In the content providing system ex100, a streaming server ex103 isconnected to the camera ex113 and others via the telephone network ex104and the base station ex109, which enables distribution of images of alive show and others. In such a distribution, a content (for example,video of a music live show) captured by the user using the camera ex113is coded as described above in each of embodiments (i.e., the camerafunctions as the image coding apparatus according to an aspect of thepresent invention), and the coded content is transmitted to thestreaming server ex103. On the other hand, the streaming server ex103carries out stream distribution of the transmitted content data to theclients upon their requests. The clients include the computer ex111, thePDA ex112, the camera ex113, the cellular phone ex114, and the gamemachine ex115 that are capable of decoding the above-mentioned codeddata. Each of the devices that have received the distributed datadecodes and reproduces the coded data (i.e., functions as the imagedecoding apparatus according to an aspect of the present invention).

The captured data may be coded by the camera ex113 or the streamingserver ex103 that transmits the data, or the coding processes may beshared between the camera ex113 and the streaming server ex103.Similarly, the distributed data may be decoded by the clients or thestreaming server ex103, or the decoding processes may be shared betweenthe clients and the streaming server ex103. Furthermore, the data of thestill images and video captured by not only the camera ex113 but alsothe camera ex116 may be transmitted to the streaming server ex103through the computer ex111. The coding processes may be performed by thecamera ex116, the computer ex111, or the streaming server ex103, orshared among them.

Furthermore, the coding and decoding processes may be performed by anLSI ex500 generally included in each of the computer ex111 and thedevices. The LSI ex500 may be configured of a single chip or a pluralityof chips. Software for coding and decoding video may be integrated intosome type of a recording medium (such as a CD-ROM, a flexible disk, anda hard disk) that is readable by the computer ex111 and others, and thecoding and decoding processes may be performed using the software.Furthermore, when the cellular phone ex114 is equipped with a camera,the video data obtained by the camera may be transmitted. The video datais data coded by the LSI ex500 included in the cellular phone ex114.

Furthermore, the streaming server ex103 may be composed of servers andcomputers, and may decentralize data and process the decentralized data,record, or distribute data.

As described above, the clients may receive and reproduce the coded datain the content providing system ex100. In other words, the clients canreceive and decode information transmitted by the user, and reproducethe decoded data in real time in the content providing system ex100, sothat the user who does not have any particular right and equipment canimplement personal broadcasting.

Aside from the example of the content providing system ex100, at leastone of the moving picture coding apparatus (image coding apparatus) andthe moving picture decoding apparatus (image decoding apparatus)described in each of embodiments may be implemented in a digitalbroadcasting system ex200 illustrated in FIG. 111. More specifically, abroadcast station ex201 communicates or transmits, via radio waves to abroadcast satellite ex202, multiplexed data obtained by multiplexingaudio data and others onto video data. The video data is data coded bythe moving picture coding method described in each of embodiments (i.e.,data coded by the image coding apparatus according to an aspect of thepresent invention). Upon receipt of the multiplexed data, the broadcastsatellite ex202 transmits radio waves for broadcasting. Then, a home-useantenna ex204 with a satellite broadcast reception function receives theradio waves. Next, a device such as a television (receiver) ex300 and aset top box (STB) ex217 decodes the received multiplexed data, andreproduces the decoded data (i.e., functions as the image decodingapparatus according to an aspect of the present invention).

Furthermore, a reader/recorder ex218 (i) reads and decodes themultiplexed data recorded on a recording medium ex215, such as a DVD anda BD, or (i) codes video signals in the recording medium ex215, and insome cases, writes data obtained by multiplexing an audio signal on thecoded data. The reader/recorder ex218 can include the moving picturedecoding apparatus or the moving picture coding apparatus as shown ineach of embodiments. In this case, the reproduced video signals aredisplayed on the monitor ex219, and can be reproduced by another deviceor system using the recording medium ex215 on which the multiplexed datais recorded. It is also possible to implement the moving picturedecoding apparatus in the set top box ex217 connected to the cable ex203for a cable television or to the antenna ex204 for satellite and/orterrestrial broadcasting, so as to display the video signals on themonitor ex219 of the television ex300. The moving picture decodingapparatus may be implemented not in the set top box but in thetelevision ex300.

FIG. 22 illustrates the television (receiver) ex300 that uses the movingpicture coding method and the moving picture decoding method describedin each of embodiments. The television ex300 includes: a tuner ex301that obtains or provides multiplexed data obtained by multiplexing audiodata onto video data, through the antenna ex204 or the cable ex203, etc.that receives a broadcast; a modulation/demodulation unit ex302 thatdemodulates the received multiplexed data or modulates data intomultiplexed data to be supplied outside; and amultiplexing/demultiplexing unit ex303 that demultiplexes the modulatedmultiplexed data into video data and audio data, or multiplexes videodata and audio data coded by a signal processing unit ex306 into data.

The television ex300 further includes: a signal processing unit ex306including an audio signal processing unit ex304 and a video signalprocessing unit ex305 that decode audio data and video data and codeaudio data and video data, respectively (which function as the imagecoding apparatus and the image decoding apparatus according to theaspects of the present invention); and an output unit ex309 including aspeaker ex307 that provides the decoded audio signal, and a display unitex308 that displays the decoded video signal, such as a display.Furthermore, the television ex300 includes an interface unit ex317including an operation input unit ex312 that receives an input of a useroperation. Furthermore, the television ex300 includes a control unitex310 that controls overall each constituent element of the televisionex300, and a power supply circuit unit ex311 that supplies power to eachof the elements. Other than the operation input unit ex312, theinterface unit ex317 may include: a bridge ex313 that is connected to anexternal device, such as the reader/recorder ex218; a slot unit ex314for enabling attachment of the recording medium ex216, such as an SDcard; a driver ex315 to be connected to an external recording medium,such as a hard disk; and a modem ex316 to be connected to a telephonenetwork. Here, the recording medium ex216 can electrically recordinformation using a non-volatile/volatile semiconductor memory elementfor storage. The constituent elements of the television ex300 areconnected to each other through a synchronous bus.

First, the configuration in which the television ex300 decodesmultiplexed data obtained from outside through the antenna ex204 andothers and reproduces the decoded data will be described. In thetelevision ex300, upon a user operation through a remote controllerex220 and others, the multiplexing/demultiplexing unit ex303demultiplexes the multiplexed data demodulated by themodulation/demodulation unit ex302, under control of the control unitex310 including a CPU. Furthermore, the audio signal processing unitex304 decodes the demultiplexed audio data, and the video signalprocessing unit ex305 decodes the demultiplexed video data, using thedecoding method described in each of embodiments, in the televisionex300. The output unit ex309 provides the decoded video signal and audiosignal outside, respectively. When the output unit ex309 provides thevideo signal and the audio signal, the signals may be temporarily storedin buffers ex318 and ex319, and others so that the signals arereproduced in synchronization with each other. Furthermore, thetelevision ex300 may read multiplexed data not through a broadcast andothers but from the recording media ex215 and ex216, such as a magneticdisk, an optical disk, and a SD card. Next, a configuration in which thetelevision ex300 codes an audio signal and a video signal, and transmitsthe data outside or writes the data on a recording medium will bedescribed. In the television ex300, upon a user operation through theremote controller ex220 and others, the audio signal processing unitex304 codes an audio signal, and the video signal processing unit ex305codes a video signal, under control of the control unit ex310 using thecoding method described in each of embodiments. Themultiplexing/demultiplexing unit ex303 multiplexes the coded videosignal and audio signal, and provides the resulting signal outside. Whenthe multiplexing/demultiplexing unit ex303 multiplexes the video signaland the audio signal, the signals may be temporarily stored in thebuffers ex320 and ex321, and others so that the signals are reproducedin synchronization with each other. Here, the buffers ex318, ex319,ex320, and ex321 may be plural as illustrated, or at least one buffermay be shared in the television ex300. Furthermore, data may be storedin a buffer so that the system overflow and underflow may be avoidedbetween the modulation/demodulation unit ex302 and themultiplexing/demultiplexing unit ex303, for example.

Furthermore, the television ex300 may include a configuration forreceiving an AV input from a microphone or a camera other than theconfiguration for obtaining audio and video data from a broadcast or arecording medium, and may code the obtained data. Although thetelevision ex300 can code, multiplex, and provide outside data in thedescription, it may be capable of only receiving, decoding, andproviding outside data but not the coding, multiplexing, and providingoutside data.

Furthermore, when the reader/recorder ex218 reads or writes multiplexeddata from or on a recording medium, one of the television ex300 and thereader/recorder ex218 may decode or code the multiplexed data, and thetelevision ex300 and the reader/recorder ex218 may share the decoding orcoding.

As an example, FIG. 23 illustrates a configuration of an informationreproducing/recording unit ex400 when data is read or written from or onan optical disk. The information reproducing/recording unit ex400includes constituent elements ex401, ex402, ex403, ex404, ex405, ex406,and ex407 to be described hereinafter. The optical head ex401 irradiatesa laser spot in a recording surface of the recording medium ex215 thatis an optical disk to write information, and detects reflected lightfrom the recording surface of the recording medium ex215 to read theinformation. The modulation recording unit ex402 electrically drives asemiconductor laser included in the optical head ex401, and modulatesthe laser light according to recorded data. The reproductiondemodulating unit ex403 amplifies a reproduction signal obtained byelectrically detecting the reflected light from the recording surfaceusing a photo detector included in the optical head ex401, anddemodulates the reproduction signal by separating a signal componentrecorded on the recording medium ex215 to reproduce the necessaryinformation. The buffer ex404 temporarily holds the information to berecorded on the recording medium ex215 and the information reproducedfrom the recording medium ex215. The disk motor ex405 rotates therecording medium ex215. The servo control unit ex406 moves the opticalhead ex401 to a predetermined information track while controlling therotation drive of the disk motor ex405 so as to follow the laser spot.The system control unit ex407 controls overall the informationreproducing/recording unit ex400. The reading and writing processes canbe implemented by the system control unit ex407 using variousinformation stored in the buffer ex404 and generating and adding newinformation as necessary, and by the modulation recording unit ex402,the reproduction demodulating unit ex403, and the servo control unitex406 that record and reproduce information through the optical headex401 while being operated in a coordinated manner. The system controlunit ex407 includes, for example, a microprocessor, and executesprocessing by causing a computer to execute a program for read andwrite.

Although the optical head ex401 irradiates a laser spot in thedescription, it may perform high-density recording using near fieldlight.

FIG. 24 illustrates the recording medium ex215 that is the optical disk.On the recording surface of the recording medium ex215, guide groovesare spirally formed, and an information track ex230 records, in advance,address information indicating an absolute position on the diskaccording to change in a shape of the guide grooves. The addressinformation includes information for determining positions of recordingblocks ex231 that are a unit for recording data. Reproducing theinformation track ex230 and reading the address information in anapparatus that records and reproduces data can lead to determination ofthe positions of the recording blocks. Furthermore, the recording mediumex215 includes a data recording area ex233, an inner circumference areaex232, and an outer circumference area ex234. The data recording areaex233 is an area for use in recording the user data. The innercircumference area ex232 and the outer circumference area ex234 that areinside and outside of the data recording area ex233, respectively arefor specific use except for recording the user data. The informationreproducing/recording unit 400 reads and writes coded audio, coded videodata, or multiplexed data obtained by multiplexing the coded audio andvideo data, from and on the data recording area ex233 of the recordingmedium ex215.

Although an optical disk having a layer, such as a DVD and a BD isdescribed as an example in the description, the optical disk is notlimited to such, and may be an optical disk having a multilayerstructure and capable of being recorded on a part other than thesurface. Furthermore, the optical disk may have a structure formultidimensional recording/reproduction, such as recording ofinformation using light of colors with different wavelengths in the sameportion of the optical disk and for recording information havingdifferent layers from various angles.

Furthermore, a car ex210 having an antenna ex205 can receive data fromthe satellite ex202 and others, and reproduce video on a display devicesuch as a car navigation system ex211 set in the car ex210, in thedigital broadcasting system ex200. Here, a configuration of the carnavigation system ex211 will be a configuration, for example, includinga GPS receiving unit from the configuration illustrated in FIG. 22. Thesame will be true for the configuration of the computer ex111, thecellular phone ex114, and others.

FIG. 25A illustrates the cellular phone ex114 that uses the movingpicture coding method and the moving picture decoding method describedin embodiments. The cellular phone ex114 includes: an antenna ex350 fortransmitting and receiving radio waves through the base station ex110; acamera unit ex365 capable of capturing moving and still images; and adisplay unit ex358 such as a liquid crystal display for displaying thedata such as decoded video captured by the camera unit ex365 or receivedby the antenna ex350. The cellular phone ex114 further includes: a mainbody unit including an operation key unit ex366; an audio output unitex357 such as a speaker for output of audio; an audio input unit ex356such as a microphone for input of audio; a memory unit ex367 for storingcaptured video or still pictures, recorded audio, coded or decoded dataof the received video, the still pictures, e-mails, or others; and aslot unit ex364 that is an interface unit for a recording medium thatstores data in the same manner as the memory unit ex367.

Next, an example of a configuration of the cellular phone ex114 will bedescribed with reference to FIG. 1158. In the cellular phone ex114, amain control unit ex360 designed to control overall each unit of themain body including the display unit ex358 as well as the operation keyunit ex366 is connected mutually, via a synchronous bus ex370, to apower supply circuit unit ex361, an operation input control unit ex362,a video signal processing unit ex355, a camera interface unit ex363, aliquid crystal display (LCD) control unit ex359, amodulation/demodulation unit ex352, a multiplexing/demultiplexing unitex353, an audio signal processing unit ex354, the slot unit ex364, andthe memory unit ex367.

When a call-end key or a power key is turned ON by a user's operation,the power supply circuit unit ex361 supplies the respective units withpower from a battery pack so as to activate the cell phone ex114.

In the cellular phone ex114, the audio signal processing unit ex354converts the audio signals collected by the audio input unit ex356 invoice conversation mode into digital audio signals under the control ofthe main control unit ex360 including a CPU, ROM, and RAM. Then, themodulation/demodulation unit ex352 performs spread spectrum processingon the digital audio signals, and the transmitting and receiving unitex351 performs digital-to-analog conversion and frequency conversion onthe data, so as to transmit the resulting data via the antenna ex350.Also, in the cellular phone ex114, the transmitting and receiving unitex351 amplifies the data received by the antenna ex350 in voiceconversation mode and performs frequency conversion and theanalog-to-digital conversion on the data. Then, themodulation/demodulation unit ex352 performs inverse spread spectrumprocessing on the data, and the audio signal processing unit ex354converts it into analog audio signals, so as to output them via theaudio output unit ex357.

Furthermore, when an e-mail in data communication mode is transmitted,text data of the e-mail inputted by operating the operation key unitex366 and others of the main body is sent out to the main control unitex360 via the operation input control unit ex362. The main control unitex360 causes the modulation/demodulation unit ex352 to perform spreadspectrum processing on the text data, and the transmitting and receivingunit ex351 performs the digital-to-analog conversion and the frequencyconversion on the resulting data to transmit the data to the basestation ex110 via the antenna ex350. When an e-mail is received,processing that is approximately inverse to the processing fortransmitting an e-mail is performed on the received data, and theresulting data is provided to the display unit ex358.

When video, still images, or video and audio in data communication modeis or are transmitted, the video signal processing unit ex355 compressesand codes video signals supplied from the camera unit ex365 using themoving picture coding method shown in each of embodiments (i.e.,functions as the image coding apparatus according to the aspect of thepresent invention), and transmits the coded video data to themultiplexing/demultiplexing unit ex353. In contrast, during when thecamera unit ex365 captures video, still images, and others, the audiosignal processing unit ex354 codes audio signals collected by the audioinput unit ex356, and transmits the coded audio data to themultiplexing/demultiplexing unit ex353.

The multiplexing/demultiplexing unit ex353 multiplexes the coded videodata supplied from the video signal processing unit ex355 and the codedaudio data supplied from the audio signal processing unit ex354, using apredetermined method. Then, the modulation/demodulation unit(modulation/demodulation circuit unit) ex352 performs spread spectrumprocessing on the multiplexed data, and the transmitting and receivingunit ex351 performs digital-to-analog conversion and frequencyconversion on the data so as to transmit the resulting data via theantenna ex350.

When receiving data of a video file which is linked to a Web page andothers in data communication mode or when receiving an e-mail with videoand/or audio attached, in order to decode the multiplexed data receivedvia the antenna ex350, the multiplexing/demultiplexing unit ex353demultiplexes the multiplexed data into a video data bit stream and anaudio data bit stream, and supplies the video signal processing unitex355 with the coded video data and the audio signal processing unitex354 with the coded audio data, through the synchronous bus ex370. Thevideo signal processing unit ex355 decodes the video signal using amoving picture decoding method corresponding to the moving picturecoding method shown in each of embodiments (i.e., functions as the imagedecoding apparatus according to the aspect of the present invention),and then the display unit ex358 displays, for instance, the video andstill images included in the video file linked to the Web page via theLCD control unit ex359. Furthermore, the audio signal processing unitex354 decodes the audio signal, and the audio output unit ex357 providesthe audio.

Furthermore, similarly to the television ex300, it is possible for aterminal such as the cellular phone ex114 to have 3 types ofimplementation configurations including not only (i) a transmitting andreceiving terminal including both a coding apparatus and a decodingapparatus, but also (ii) a transmitting terminal including only a codingapparatus and (iii) a receiving terminal including only a decodingapparatus. Although the digital broadcasting system ex200 receives andtransmits the multiplexed data obtained by multiplexing audio data ontovideo data in the description, the multiplexed data may be data obtainedby multiplexing not audio data but character data related to video ontovideo data, and may be not multiplexed data but video data itself.

As such, the moving picture coding method and the moving picturedecoding method in each of embodiments can be used in any of the devicesand systems described. Thus, the advantages described in each ofembodiments can be obtained.

Furthermore, the present invention is not limited to embodiments, andvarious modifications and revisions are possible without departing fromthe scope of the present invention.

Embodiment 4

Video data can be generated by switching, as necessary, between (i) themoving picture coding method or the moving picture coding apparatusshown in each of embodiments and (ii) a moving picture coding method ora moving picture coding apparatus in conformity with a differentstandard, such as MPEG-2, MPEG-4 AVC, and VC-1.

Here, when a plurality of video data that conforms to the differentstandards is generated and is then decoded, the decoding methods need tobe selected to conform to the different standards. However, since thestandard to which each of the plurality of the video data to be decodedconforms cannot be detected, there is a problem that an appropriatedecoding method cannot be selected.

In order to solve the problem, multiplexed data obtained by multiplexingaudio data and others onto video data has a structure includingidentification information indicating to which standard the video dataconforms. The specific structure of the multiplexed data including thevideo data generated in the moving picture coding method and by themoving picture coding apparatus shown in each of embodiments will behereinafter described. The multiplexed data is a digital stream in theMPEG-2 Transport Stream format.

FIG. 26 illustrates a structure of the multiplexed data. As illustratedin FIG. 26, the multiplexed data can be obtained by multiplexing atleast one of a video stream, an audio stream, a presentation graphicsstream (PG), and an interactive graphics stream. The video streamrepresents primary video and secondary video of a movie, the audiostream (IG) represents a primary audio part and a secondary audio partto be mixed with the primary audio part, and the presentation graphicsstream represents subtitles of the movie. Here, the primary video isnormal video to be displayed on a screen, and the secondary video isvideo to be displayed on a smaller window in the primary video.Furthermore, the interactive graphics stream represents an interactivescreen to be generated by arranging the GUI components on a screen. Thevideo stream is coded in the moving picture coding method or by themoving picture coding apparatus shown in each of embodiments, or in amoving picture coding method or by a moving picture coding apparatus inconformity with a conventional standard, such as MPEG-2, MPEG-4 AVC, andVC-1. The audio stream is coded in accordance with a standard, such asDolby-AC-3, Dolby Digital Plus, MLP, DTS, DTS-HD, and linear PCM.

Each stream included in the multiplexed data is identified by PID. Forexample, 0x1011 is allocated to the video stream to be used for video ofa movie, 0x1100 to 0x111F are allocated to the audio streams, 0x1200 to0x121F are allocated to the presentation graphics streams, 0x1400 to0x141F are allocated to the interactive graphics streams, 0x1B00 to0x1B1F are allocated to the video streams to be used for secondary videoof the movie, and 0x1A00 to 0x1A1F are allocated to the audio streams tobe used for the secondary audio to be mixed with the primary audio.

FIG. 27 schematically illustrates how data is multiplexed. First, avideo stream ex235 composed of video frames and an audio stream ex238composed of audio frames are transformed into a stream of PES packetsex236 and a stream of PES packets ex239, and further into TS packetsex237 and TS packets ex240, respectively. Similarly, data of apresentation graphics stream ex241 and data of an interactive graphicsstream ex244 are transformed into a stream of PES packets ex242 and astream of PES packets ex245, and further into TS packets ex243 and TSpackets ex246, respectively. These TS packets are multiplexed into astream to obtain multiplexed data ex247.

FIG. 28 illustrates how a video stream is stored in a stream of PESpackets in more detail. The first bar in FIG. 28 shows a video framestream in a video stream. The second bar shows the stream of PESpackets. As indicated by arrows denoted as yy1, yy2, yy3, and yy4 inFIG. 28, the video stream is divided into pictures as I pictures, Bpictures, and P pictures each of which is a video presentation unit, andthe pictures are stored in a payload of each of the PES packets. Each ofthe PES packets has a PES header, and the PES header stores aPresentation Time-Stamp (PTS) indicating a display time of the picture,and a Decoding Time-Stamp (DTS) indicating a decoding time of thepicture.

FIG. 29 illustrates a format of TS packets to be finally written on themultiplexed data. Each of the TS packets is a 188-byte fixed lengthpacket including a 4-byte TS header having information, such as a PIDfor identifying a stream and a 184-byte TS payload for storing data. ThePES packets are divided, and stored in the TS payloads, respectively.When a BD ROM is used, each of the TS packets is given a 4-byteTP_Extra_Header, thus resulting in 192-byte source packets. The sourcepackets are written on the multiplexed data. The TP_Extra_Header storesinformation such as an Arrival_Time_Stamp (ATS). The ATS shows atransfer start time at which each of the TS packets is to be transferredto a PID filter. The source packets are arranged in the multiplexed dataas shown at the bottom of FIG. 29. The numbers incrementing from thehead of the multiplexed data are called source packet numbers (SPNs).

Each of the TS packets included in the multiplexed data includes notonly streams of audio, video, subtitles and others, but also a ProgramAssociation Table (PAT), a Program Map Table (PMT), and a Program ClockReference (PCR). The PAT shows what a PID in a PMT used in themultiplexed data indicates, and a PID of the PAT itself is registered aszero. The PMT stores PIDs of the streams of video, audio, subtitles andothers included in the multiplexed data, and attribute information ofthe streams corresponding to the PIDs. The PMT also has variousdescriptors relating to the multiplexed data. The descriptors haveinformation such as copy control information showing whether copying ofthe multiplexed data is permitted or not. The PCR stores STC timeinformation corresponding to an ATS showing when the PCR packet istransferred to a decoder, in order to achieve synchronization between anArrival Time Clock (ATC) that is a time axis of ATSs, and an System TimeClock (STC) that is a time axis of PTSs and DTSs.

FIG. 30 illustrates the data structure of the PMT in detail. A PMTheader is disposed at the top of the PMT. The PMT header describes thelength of data included in the PMT and others. A plurality ofdescriptors relating to the multiplexed data is disposed after the PMTheader. Information such as the copy control information is described inthe descriptors. After the descriptors, a plurality of pieces of streaminformation relating to the streams included in the multiplexed data isdisposed. Each piece of stream information includes stream descriptorseach describing information, such as a stream type for identifying acompression codec of a stream, a stream PID, and stream attributeinformation (such as a frame rate or an aspect ratio). The streamdescriptors are equal in number to the number of streams in themultiplexed data.

When the multiplexed data is recorded on a recording medium and others,it is recorded together with multiplexed data information files.

Each of the multiplexed data information files is management informationof the multiplexed data as shown in FIG. 31. The multiplexed datainformation files are in one to one correspondence with the multiplexeddata, and each of the files includes multiplexed data information,stream attribute information, and an entry map.

As illustrated in FIG. 31, the multiplexed data information includes asystem rate, a reproduction start time, and a reproduction end time. Thesystem rate indicates the maximum transfer rate at which a system targetdecoder to be described later transfers the multiplexed data to a PIDfilter. The intervals of the ATSs included in the multiplexed data areset to not higher than a system rate. The reproduction start timeindicates a PTS in a video frame at the head of the multiplexed data. Aninterval of one frame is added to a PTS in a video frame at the end ofthe multiplexed data, and the PTS is set to the reproduction end time.

As shown in FIG. 32, a piece of attribute information is registered inthe stream attribute information, for each PID of each stream includedin the multiplexed data. Each piece of attribute information hasdifferent information depending on whether the corresponding stream is avideo stream, an audio stream, a presentation graphics stream, or aninteractive graphics stream. Each piece of video stream attributeinformation carries information including what kind of compression codecis used for compressing the video stream, and the resolution, aspectratio and frame rate of the pieces of picture data that is included inthe video stream. Each piece of audio stream attribute informationcarries information including what kind of compression codec is used forcompressing the audio stream, how many channels are included in theaudio stream, which language the audio stream supports, and how high thesampling frequency is. The video stream attribute information and theaudio stream attribute information are used for initialization of adecoder before the player plays back the information.

In the present embodiment, the multiplexed data to be used is of astream type included in the PMT. Furthermore, when the multiplexed datais recorded on a recording medium, the video stream attributeinformation included in the multiplexed data information is used. Morespecifically, the moving picture coding method or the moving picturecoding apparatus described in each of embodiments includes a step or aunit for allocating unique information indicating video data generatedby the moving picture coding method or the moving picture codingapparatus in each of embodiments, to the stream type included in the PMTor the video stream attribute information. With the configuration, thevideo data generated by the moving picture coding method or the movingpicture coding apparatus described in each of embodiments can bedistinguished from video data that conforms to another standard.

Furthermore, FIG. 33 illustrates steps of the moving picture decodingmethod according to the present embodiment. In Step exS100, the streamtype included in the PMT or the video stream attribute informationincluded in the multiplexed data information is obtained from themultiplexed data. Next, in Step exS101, it is determined whether or notthe stream type or the video stream attribute information indicates thatthe multiplexed data is generated by the moving picture coding method orthe moving picture coding apparatus in each of embodiments. When it isdetermined that the stream type or the video stream attributeinformation indicates that the multiplexed data is generated by themoving picture coding method or the moving picture coding apparatus ineach of embodiments, in Step exS102, decoding is performed by the movingpicture decoding method in each of embodiments. Furthermore, when thestream type or the video stream attribute information indicatesconformance to the conventional standards, such as MPEG-2, MPEG-4 AVC,and VC-1, in Step exS103, decoding is performed by a moving picturedecoding method in conformity with the conventional standards.

As such, allocating a new unique value to the stream type or the videostream attribute information enables determination whether or not themoving picture decoding method or the moving picture decoding apparatusthat is described in each of embodiments can perform decoding. Even whenmultiplexed data that conforms to a different standard is input, anappropriate decoding method or apparatus can be selected. Thus, itbecomes possible to decode information without any error. Furthermore,the moving picture coding method or apparatus, or the moving picturedecoding method or apparatus in the present embodiment can be used inthe devices and systems described above.

Embodiment 5

Each of the moving picture coding method, the moving picture codingapparatus, the moving picture decoding method, and the moving picturedecoding apparatus in each of embodiments is typically achieved in theform of an integrated circuit or a Large Scale Integrated (LSI) circuit.As an example of the LSI, FIG. 34 illustrates a configuration of the LSIex500 that is made into one chip. The LSI ex500 includes elements ex501,ex502, ex503, ex504, ex505, ex506, ex507, ex508, and ex509 to bedescribed below, and the elements are connected to each other through abus ex510. The power supply circuit unit ex505 is activated by supplyingeach of the elements with power when the power supply circuit unit ex505is turned on.

For example, when coding is performed, the LSI ex500 receives an AVsignal from a microphone ex117, a camera ex113, and others through an AVIO ex509 under control of a control unit ex501 including a CPU ex502, amemory controller ex503, a stream controller ex504, and a drivingfrequency control unit ex512. The received AV signal is temporarilystored in an external memory ex511, such as an SDRAM. Under control ofthe control unit ex501, the stored data is segmented into data portionsaccording to the processing amount and speed to be transmitted to asignal processing unit ex507. Then, the signal processing unit ex507codes an audio signal and/or a video signal. Here, the coding of thevideo signal is the coding described in each of embodiments.Furthermore, the signal processing unit ex507 sometimes multiplexes thecoded audio data and the coded video data, and a stream IO ex506provides the multiplexed data outside. The provided multiplexed data istransmitted to the base station ex107, or written on the recordingmedium ex215. When data sets are multiplexed, the data should betemporarily stored in the buffer ex508 so that the data sets aresynchronized with each other.

Although the memory ex511 is an element outside the LSI ex500, it may beincluded in the LSI ex500. The buffer ex508 is not limited to onebuffer, but may be composed of buffers. Furthermore, the LSI ex500 maybe made into one chip or a plurality of chips.

Furthermore, although the control unit ex501 includes the CPU ex502, thememory controller ex503, the stream controller ex504, the drivingfrequency control unit ex512, the configuration of the control unitex501 is not limited to such. For example, the signal processing unitex507 may further include a CPU. Inclusion of another CPU in the signalprocessing unit ex507 can improve the processing speed. Furthermore, asanother example, the CPU ex502 may serve as or be a part of the signalprocessing unit ex507, and, for example, may include an audio signalprocessing unit. In such a case, the control unit ex501 includes thesignal processing unit ex507 or the CPU ex502 including a part of thesignal processing unit ex507.

The name used here is LSI, but it may also be called IC, system LSI,super LSI, or ultra LSI depending on the degree of integration.

Moreover, ways to achieve integration are not limited to the LSI, and aspecial circuit or a general purpose processor and so forth can alsoachieve the integration. Field Programmable Gate Array (FPGA) that canbe programmed after manufacturing LSIs or a reconfigurable processorthat allows re-configuration of the connection or configuration of anLSI can be used for the same purpose. Such a programmable logic devicecan typically execute the moving picture coding method and/or the movingpicture decoding method according to any of the above embodiments, byloading or reading from a memory or the like one or more programs thatare included in software or firmware.

In the future, with advancement in semiconductor technology, a brand-newtechnology may replace LSI. The functional blocks can be integratedusing such a technology. The possibility is that the present inventionis applied to biotechnology.

Embodiment 6

When video data generated in the moving picture coding method or by themoving picture coding apparatus described in each of embodiments isdecoded, it is possible for the processing amount to increase comparedto when video data that conforms to a conventional standard, such asMPEG-2, MPEG-4 AVC, and VC-1 is decoded. Thus, the LSI ex500 needs to beset to a driving frequency higher than that of the CPU ex502 to be usedwhen video data in conformity with the conventional standard is decoded.However, when the driving frequency is set higher, there is a problemthat the power consumption increases.

In order to solve the problem, the moving picture decoding apparatus,such as the television ex300 and the LSI ex500 is configured todetermine to which standard the video data conforms, and switch betweenthe driving frequencies according to the determined standard. FIG. 35illustrates a configuration ex800 in the present embodiment. A drivingfrequency switching unit ex803 sets a driving frequency to a higherdriving frequency when video data is generated by the moving picturecoding method or the moving picture coding apparatus described in eachof embodiments. Then, the driving frequency switching unit ex803instructs a decoding processing unit ex801 that executes the movingpicture decoding method described in each of embodiments to decode thevideo data. When the video data conforms to the conventional standard,the driving frequency switching unit ex803 sets a driving frequency to alower driving frequency than that of the video data generated by themoving picture coding method or the moving picture coding apparatusdescribed in each of embodiments. Then, the driving frequency switchingunit ex803 instructs the decoding processing unit ex802 that conforms tothe conventional standard to decode the video data.

More specifically, the driving frequency switching unit ex803 includesthe CPU ex502 and the driving frequency control unit ex512 in FIG. 34.Here, each of the decoding processing unit ex801 that executes themoving picture decoding method described in each of embodiments and thedecoding processing unit ex802 that conforms to the conventionalstandard corresponds to the signal processing unit ex507 in FIG. 34. TheCPU ex502 determines to which standard the video data conforms. Then,the driving frequency control unit ex512 determines a driving frequencybased on a signal from the CPU ex502. Furthermore, the signal processingunit ex507 decodes the video data based on the signal from the CPUex502. For example, it is possible that the identification informationdescribed in Embodiment 4 is used for identifying the video data. Theidentification information is not limited to the one described inEmbodiment 4 but may be any information as long as the informationindicates to which standard the video data conforms. For example, whenwhich standard video data conforms to can be determined based on anexternal signal for determining that the video data is used for atelevision or a disk, etc., the determination may be made based on suchan external signal. Furthermore, the CPU ex502 selects a drivingfrequency based on, for example, a look-up table in which the standardsof the video data are associated with the driving frequencies as shownin FIG. 37. The driving frequency can be selected by storing the look-uptable in the buffer ex508 and in an internal memory of an LSI, and withreference to the look-up table by the CPU ex502.

FIG. 36 illustrates steps for executing a method in the presentembodiment. First, in Step exS200, the signal processing unit ex507obtains identification information from the multiplexed data. Next, inStep exS201, the CPU ex502 determines whether or not the video data isgenerated by the coding method and the coding apparatus described ineach of embodiments, based on the identification information. When thevideo data is generated by the moving picture coding method and themoving picture coding apparatus described in each of embodiments, inStep exS202, the CPU ex502 transmits a signal for setting the drivingfrequency to a higher driving frequency to the driving frequency controlunit ex512. Then, the driving frequency control unit ex512 sets thedriving frequency to the higher driving frequency. On the other hand,when the identification information indicates that the video dataconforms to the conventional standard, such as MPEG-2, MPEG-4 AVC, andVC-1, in Step exS203, the CPU ex502 transmits a signal for setting thedriving frequency to a lower driving frequency to the driving frequencycontrol unit ex512. Then, the driving frequency control unit ex512 setsthe driving frequency to the lower driving frequency than that in thecase where the video data is generated by the moving picture codingmethod and the moving picture coding apparatus described in each ofembodiment.

Furthermore, along with the switching of the driving frequencies, thepower conservation effect can be improved by changing the voltage to beapplied to the LSI ex500 or an apparatus including the LSI ex500. Forexample, when the driving frequency is set lower, it is possible thatthe voltage to be applied to the LSI ex500 or the apparatus includingthe LSI ex500 is set to a voltage lower than that in the case where thedriving frequency is set higher.

Furthermore, when the processing amount for decoding is larger, thedriving frequency may be set higher, and when the processing amount fordecoding is smaller, the driving frequency may be set lower as themethod for setting the driving frequency. Thus, the setting method isnot limited to the ones described above. For example, when theprocessing amount for decoding video data in conformity with MPEG-4 AVCis larger than the processing amount for decoding video data generatedby the moving picture coding method and the moving picture codingapparatus described in each of embodiments, it is possible that thedriving frequency is set in reverse order to the setting describedabove.

Furthermore, the method for setting the driving frequency is not limitedto the method for setting the driving frequency lower. For example, whenthe identification information indicates that the video data isgenerated by the moving picture coding method and the moving picturecoding apparatus described in each of embodiments, it is possible thatthe voltage to be applied to the LSI ex500 or the apparatus includingthe LSI ex500 is set higher. When the identification informationindicates that the video data conforms to the conventional standard,such as MPEG-2, MPEG-4 AVC, and VC-1, it is possible that the voltage tobe applied to the LSI ex500 or the apparatus including the LSI ex500 isset lower. As another example, it is possible that, when theidentification information indicates that the video data is generated bythe moving picture coding method and the moving picture coding apparatusdescribed in each of embodiments, the driving of the CPU ex502 is notsuspended, and when the identification information indicates that thevideo data conforms to the conventional standard, such as MPEG-2, MPEG-4AVC, and VC-1, the driving of the CPU ex502 is suspended at a given timebecause the CPU ex502 has extra processing capacity. It is possiblethat, even when the identification information indicates that the videodata is generated by the moving picture coding method and the movingpicture coding apparatus described in each of embodiments, in the casewhere the CPU ex502 has extra processing capacity, the driving of theCPU ex502 is suspended at a given time. In such a case, it is possiblethat the suspending time is set shorter than that in the case where whenthe identification information indicates that the video data conforms tothe conventional standard, such as MPEG-2, MPEG-4 AVC, and VC-1.

Accordingly, the power conservation effect can be improved by switchingbetween the driving frequencies in accordance with the standard to whichthe video data conforms. Furthermore, when the LSI ex500 or theapparatus including the LSI ex500 is driven using a battery, the batterylife can be extended with the power conservation effect.

Embodiment 7

There are cases where a plurality of video data that conforms todifferent standards, is provided to the devices and systems, such as atelevision and a cellular phone. In order to enable decoding theplurality of video data that conforms to the different standards, thesignal processing unit ex507 of the LSI ex500 needs to conform to thedifferent standards. However, the problems of increase in the scale ofthe circuit of the LSI ex500 and increase in the cost arise with theindividual use of the signal processing units ex507 that conform to therespective standards.

In order to solve the problem, what is conceived is a configuration inwhich the decoding processing unit for implementing the moving picturedecoding method described in each of embodiments and the decodingprocessing unit that conforms to the conventional standard, such asMPEG-2, MPEG-4 AVC, and VC-1 are partly shared. Ex900 in FIG. 38A showsan example of the configuration. For example, the moving picturedecoding method described in each of embodiments and the moving picturedecoding method that conforms to MPEG-4 AVC have, partly in common, thedetails of processing, such as entropy coding, inverse quantization,deblocking filtering, and motion compensated prediction. It is possiblefor a decoding processing unit ex902 that conforms to MPEG-4 AVC to beshared by common processing operations, and for a dedicated decodingprocessing unit ex901 to be used for processing which is unique to anaspect of the present invention and does not conform to MPEG-4 AVC. Inparticular, since the aspect of the present invention is characterizedby inverse quantization, it is possible, for example, for the dedicateddecoding processing unit ex901 to be used for inverse quantization, andfor the decoding processing unit to be shared by any or all of the otherprocessing, such as entropy decoding, deblocking filtering, and motioncompensation. The decoding processing unit for implementing the movingpicture decoding method described in each of embodiments may be sharedfor the processing to be shared, and a dedicated decoding processingunit may be used for processing unique to that of MPEG-4 AVC.

Furthermore, ex1000 in FIG. 38B shows another example in that processingis partly shared. This example uses a configuration including adedicated decoding processing unit ex1001 that supports the processingunique to an aspect of the present invention, a dedicated decodingprocessing unit ex1002 that supports the processing unique to anotherconventional standard, and a decoding processing unit ex1003 thatsupports processing to be shared between the moving picture decodingmethod according to the aspect of the present invention and theconventional moving picture decoding method. Here, the dedicateddecoding processing units ex1001 and ex1002 are not necessarilyspecialized for the processing according to the aspect of the presentinvention and the processing of the conventional standard, respectively,and may be the ones capable of implementing general processing.Furthermore, the configuration of the present embodiment can beimplemented by the LSI ex500.

As such, reducing the scale of the circuit of an LSI and reducing thecost are possible by sharing the decoding processing unit for theprocessing to be shared between the moving picture decoding methodaccording to the aspect of the present invention and the moving picturedecoding method in conformity with the conventional standard.

Although only some exemplary embodiments of the present invention havebeen described in detail above, those skilled in the art will readilyappreciate that many modifications are possible in the exemplaryembodiments without materially departing from the novel teachings andadvantages of the present invention. Accordingly, all such modificationsare intended to be included within the scope of the present invention.

INDUSTRIAL APPLICABILITY

The image coding method and the image decoding method according to thepresent disclosure are applicable to any type of multimedia data. Theimage coding method and the image decoding method according to thepresent disclosure are useful methods for use in storage, transmission,and communication of data using, for example, mobile phones, DVDsystems, or personal computers.

1. An image decoding method of decoding an image from a coded bitstream,the image including one or more transform blocks each having a lumacomponent and a chroma component, the luma component being to beprocessed on a basis of a luma block which belongs to a current one ofthe one or more transform blocks and has a same size as a size of thecurrent transform block, the chroma component being to be processed on abasis of a chroma block which belongs to a current one of the one ormore transform blocks and has a size smaller than a size of the lumablock, and the image decoding method comprising: decoding coefficientsof the luma component and coefficients of the chroma component which arecoded and included in the coded bitstream; and deriving the lumacomponent by performing transform on the coefficients of the lumacomponent and deriving the chroma component by performing transform onthe coefficients of the chroma component, wherein in the deriving, whenthe size of the current transform block is a predetermined first minimumsize, the chroma component is derived by performing the transform on thecoefficients of the chroma component on a basis of a block resultingfrom binding a plurality of the chroma blocks, the resulting blockhaving a same size as the size of the luma block, and in the decoding,when the size of the current transform block is the first minimum size,a flag indicating whether the coefficients of the chroma componentinclude a non-zero coefficient is not decoded.
 2. An image decodingapparatus which decodes an image from a coded bitstream, the imageincluding one or more transform blocks each having a luma component anda chroma component, the luma component being to be processed on a basisof a luma block which belongs to a current one of the one or moretransform blocks and has a same size as a size of the current transformblock, the chroma component being to be processed on a basis of a chromablock which belongs to a current one of the one or more transform blocksand has a size smaller than a size of the luma block, and the imagedecoding apparatus comprising: a decoding unit which decodescoefficients of the luma component and coefficients of the chromacomponent which are coded and included in the coded bitstream; and aderiving unit which derives the luma component by performing transformon the coefficients of the luma component and derives the chromacomponent by performing transform on the coefficients of the chromacomponent, wherein the deriving unit derives, when the size of thecurrent transform block is a predetermined first minimum size, thechroma component by performing the transform on the coefficients of thechroma component on a basis of a block resulting from binding aplurality of the chroma blocks, the resulting block having a same sizeas the size of the luma block, and the decoding unit does not decode,when the size of the current transform block is the first minimum size,a flag indicating whether the coefficients of the chroma componentinclude a non-zero coefficient.
 3. An image decoding apparatus whichdecodes an image from a coded bitstream, the image including one or moretransform blocks each having a luma component and a chroma component,the luma component being to be processed on a basis of a luma blockwhich belongs to a current one of the one or more transform blocks andhas a same size as a size of the current transform block, the chromacomponent being to be processed on a basis of a chroma block whichbelongs to a current one of the one or more transform blocks and has asize smaller than a size of the luma block, and the image decodingapparatus comprising: processing circuitry; and storage coupled to theprocessing circuitry, wherein the processing circuitry performs thefollowing using the storage: decoding coefficients of the luma componentand coefficients of the chroma component which are coded and included inthe coded bitstream; and deriving the luma component by performingtransform on the coefficients of the luma component and deriving thechroma component by performing transform on the coefficients of thechroma component, wherein in the deriving, when the size of the currenttransform block is a predetermined first minimum size, the chromacomponent is derived by performing the transform on the coefficients ofthe chroma component on a basis of a block resulting from binding aplurality of the chroma blocks, the resulting block having a same sizeas the size of the luma block, and in the decoding, when the size of thecurrent transform block is the first minimum size, a flag indicatingwhether the coefficients of the chroma component include a non-zerocoefficient is not decoded.